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[PATCH v24 1/5] sequential scan for dshash 230+ messages / 3 participants [nested] [flat]
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2018-06-29 07:41 UTC (permalink / raw) Add sequential scan feature to dshash. --- src/backend/lib/dshash.c | 185 +++++++++++++++++++++++++++++++++++++-- src/include/lib/dshash.h | 22 ++++- 2 files changed, 201 insertions(+), 6 deletions(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index fbdd941325..7675370058 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -112,6 +112,7 @@ struct dshash_table size_t size_log2; /* log2(number of buckets) */ bool find_locked; /* Is any partition lock held by 'find'? */ bool find_exclusively_locked; /* ... exclusively? */ + bool seqscan_running;/* now under sequential scan */ }; /* Given a pointer to an item, find the entry (user data) it holds. */ @@ -127,6 +128,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +158,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -228,6 +237,7 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg) hash_table->find_locked = false; hash_table->find_exclusively_locked = false; + hash_table->seqscan_running = false; /* * Set up the initial array of buckets. Our initial size is the same as @@ -279,6 +289,7 @@ dshash_attach(dsa_area *area, const dshash_parameters *params, hash_table->control = dsa_get_address(area, control); hash_table->find_locked = false; hash_table->find_exclusively_locked = false; + hash_table->seqscan_running = false; Assert(hash_table->control->magic == DSHASH_MAGIC); /* @@ -324,7 +335,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -549,9 +560,14 @@ dshash_delete_entry(dshash_table *hash_table, void *entry) LW_EXCLUSIVE)); delete_item(hash_table, item); - hash_table->find_locked = false; - hash_table->find_exclusively_locked = false; - LWLockRelease(PARTITION_LOCK(hash_table, partition)); + + /* We need to keep partition lock while sequential scan */ + if (!hash_table->seqscan_running) + { + hash_table->find_locked = false; + hash_table->find_exclusively_locked = false; + LWLockRelease(PARTITION_LOCK(hash_table, partition)); + } } /* @@ -568,6 +584,8 @@ dshash_release_lock(dshash_table *hash_table, void *entry) Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition_index), hash_table->find_exclusively_locked ? LW_EXCLUSIVE : LW_SHARED)); + /* lock is under control of sequential scan */ + Assert(!hash_table->seqscan_running); hash_table->find_locked = false; hash_table->find_exclusively_locked = false; @@ -592,6 +610,164 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan trhough dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should be called for incomplete scans and otherwise + * shoudln't. Finished scans are cleaned up automatically. + * + * Returned elements are locked as is the case with dshash_find. However, the + * caller must not release the lock. + * + * Same as dynanash, the caller may delete returned elements midst of a scan. + * + * If consistent is set for dshash_seq_init, the all hash table partitions are + * locked in the requested mode (as determined by the exclusive flag) during + * the scan. Otherwise partitions are locked in one-at-a-time way during the + * scan. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool consistent, bool exclusive) +{ + /* allowed at most one scan at once */ + Assert(!hash_table->seqscan_running); + + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->consistent = consistent; + status->exclusive = exclusive; + hash_table->seqscan_running = true; + + /* + * Protect all partitions from modification if the caller wants a + * consistent result. + */ + if (consistent) + { + int i; + + for (i = 0; i < DSHASH_NUM_PARTITIONS; ++i) + { + Assert(!LWLockHeldByMe(PARTITION_LOCK(hash_table, i))); + + LWLockAcquire(PARTITION_LOCK(hash_table, i), + exclusive ? LW_EXCLUSIVE : LW_SHARED); + } + ensure_valid_bucket_pointers(hash_table); + } +} + +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + Assert(status->hash_table->seqscan_running); + if (status->curitem == NULL) + { + int partition; + + Assert (status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + if (!status->consistent) + { + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finsih. */ + dshash_seq_term(status); + return NULL; + } + + /* Also move parititon lock if needed */ + if (!status->consistent) + { + int next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + /* Move lock along with partition for the bucket */ + if (status->curpartition != next_partition) + { + /* + * Lock the next partition then release the current, not in the + * reverse order to to avoid concurrent resizing. Partitions + * are locked in the same order with resize() so dead locks + * won't happen. + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +void +dshash_seq_term(dshash_seq_status *status) +{ + Assert(status->hash_table->seqscan_running); + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + status->hash_table->seqscan_running = false; + + if (status->consistent) + { + int i; + + for (i = 0; i < DSHASH_NUM_PARTITIONS; ++i) + LWLockRelease(PARTITION_LOCK(status->hash_table, i)); + } + else if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. @@ -673,7 +849,6 @@ delete_item(dshash_table *hash_table, dshash_table_item *item) /* * Grow the hash table if necessary to the requested number of buckets. The * requested size must be double some previously observed size. - * * Must be called without any partition lock held. */ static void diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..ad88f32cdd 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,22 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; + int curbucket; + int nbuckets; + dshash_table_item *curitem; + dsa_pointer pnextitem; + int curpartition; + bool consistent; + bool exclusive; +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -70,7 +86,6 @@ extern dshash_table *dshash_attach(dsa_area *area, extern void dshash_detach(dshash_table *hash_table); extern dshash_table_handle dshash_get_hash_table_handle(dshash_table *hash_table); extern void dshash_destroy(dshash_table *hash_table); - /* Finding, creating, deleting entries. */ extern void *dshash_find(dshash_table *hash_table, const void *key, bool exclusive); @@ -80,6 +95,11 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool consistent, bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.23.0 ----Next_Part(Wed_Jan_22_17_24_04_2020_620)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v24 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2018-06-29 07:41 UTC (permalink / raw) Add sequential scan feature to dshash. --- src/backend/lib/dshash.c | 188 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 23 ++++- 2 files changed, 206 insertions(+), 5 deletions(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 350f8c0a66..4f0c7ec840 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -112,6 +112,7 @@ struct dshash_table size_t size_log2; /* log2(number of buckets) */ bool find_locked; /* Is any partition lock held by 'find'? */ bool find_exclusively_locked; /* ... exclusively? */ + bool seqscan_running;/* now under sequential scan */ }; /* Given a pointer to an item, find the entry (user data) it holds. */ @@ -127,6 +128,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +158,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -228,6 +237,7 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg) hash_table->find_locked = false; hash_table->find_exclusively_locked = false; + hash_table->seqscan_running = false; /* * Set up the initial array of buckets. Our initial size is the same as @@ -279,6 +289,7 @@ dshash_attach(dsa_area *area, const dshash_parameters *params, hash_table->control = dsa_get_address(area, control); hash_table->find_locked = false; hash_table->find_exclusively_locked = false; + hash_table->seqscan_running = false; Assert(hash_table->control->magic == DSHASH_MAGIC); /* @@ -324,7 +335,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -549,9 +560,14 @@ dshash_delete_entry(dshash_table *hash_table, void *entry) LW_EXCLUSIVE)); delete_item(hash_table, item); - hash_table->find_locked = false; - hash_table->find_exclusively_locked = false; - LWLockRelease(PARTITION_LOCK(hash_table, partition)); + + /* We need to keep partition lock while sequential scan */ + if (!hash_table->seqscan_running) + { + hash_table->find_locked = false; + hash_table->find_exclusively_locked = false; + LWLockRelease(PARTITION_LOCK(hash_table, partition)); + } } /* @@ -568,6 +584,8 @@ dshash_release_lock(dshash_table *hash_table, void *entry) Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition_index), hash_table->find_exclusively_locked ? LW_EXCLUSIVE : LW_SHARED)); + /* lock is under control of sequential scan */ + Assert(!hash_table->seqscan_running); hash_table->find_locked = false; hash_table->find_exclusively_locked = false; @@ -592,6 +610,168 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan trhough dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should be called if and only if the scan is abandoned + * before completion; if dshash_seq_next returns NULL then it has already done + * the end-of-scan cleanup. + * + * On returning element, it is locked as is the case with dshash_find. + * However, the caller must not release the lock. The lock is released as + * necessary in continued scan. + * + * As opposed to the equivalent for dynanash, the caller is not supposed to + * delete the returned element before continuing the scan. + * + * If consistent is set for dshash_seq_init, the whole hash table is + * non-exclusively locked. Otherwise a part of the hash table is locked in the + * same mode (partition lock). + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool consistent, bool exclusive) +{ + /* allowed at most one scan at once */ + Assert(!hash_table->seqscan_running); + + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->consistent = consistent; + status->exclusive = exclusive; + hash_table->seqscan_running = true; + + /* + * Protect all partitions from modification if the caller wants a + * consistent result. + */ + if (consistent) + { + int i; + + for (i = 0; i < DSHASH_NUM_PARTITIONS; ++i) + { + Assert(!LWLockHeldByMe(PARTITION_LOCK(hash_table, i))); + + LWLockAcquire(PARTITION_LOCK(hash_table, i), + exclusive ? LW_EXCLUSIVE : LW_SHARED); + } + ensure_valid_bucket_pointers(hash_table); + } +} + +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + Assert(status->hash_table->seqscan_running); + if (status->curitem == NULL) + { + int partition; + + Assert (status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + if (!status->consistent) + { + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finsih. */ + dshash_seq_term(status); + return NULL; + } + + /* Also move parititon lock if needed */ + if (!status->consistent) + { + int next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + /* Move lock along with partition for the bucket */ + if (status->curpartition != next_partition) + { + /* + * Take lock on the next partition then release the current, + * not in the reverse order. This is required to avoid + * resizing from happening during a sequential scan. Locks are + * taken in partition order so no dead lock happen with other + * seq scans or resizing. + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * This item can be deleted by the caller. Store the next item for the + * next iteration for the occasion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +void +dshash_seq_term(dshash_seq_status *status) +{ + Assert(status->hash_table->seqscan_running); + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + status->hash_table->seqscan_running = false; + + if (status->consistent) + { + int i; + + for (i = 0; i < DSHASH_NUM_PARTITIONS; ++i) + LWLockRelease(PARTITION_LOCK(status->hash_table, i)); + } + else if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index fa2e28ff3e..79698a6ad6 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,23 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state of dshash. The detail is exposed since the storage + * size should be known to users but it should be considered as an opaque + * type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; + int curbucket; + int nbuckets; + dshash_table_item *curitem; + dsa_pointer pnextitem; + int curpartition; + bool consistent; + bool exclusive; +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -70,7 +87,6 @@ extern dshash_table *dshash_attach(dsa_area *area, extern void dshash_detach(dshash_table *hash_table); extern dshash_table_handle dshash_get_hash_table_handle(dshash_table *hash_table); extern void dshash_destroy(dshash_table *hash_table); - /* Finding, creating, deleting entries. */ extern void *dshash_find(dshash_table *hash_table, const void *key, bool exclusive); @@ -80,6 +96,11 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool consistent, bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.23.0 ----Next_Part(Tue_Dec__3_17_27_59_2019_887)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v24-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v27 9/9] Add documentations about Incremental View Maintenance @ 2019-12-20 01:25 Yugo Nagata <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Yugo Nagata @ 2019-12-20 01:25 UTC (permalink / raw) --- doc/src/sgml/catalogs.sgml | 24 +- .../sgml/ref/create_materialized_view.sgml | 131 +++++- .../sgml/ref/refresh_materialized_view.sgml | 8 +- doc/src/sgml/rules.sgml | 443 ++++++++++++++++++ 4 files changed, 601 insertions(+), 5 deletions(-) diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml index a533a2153e..2561faa163 100644 --- a/doc/src/sgml/catalogs.sgml +++ b/doc/src/sgml/catalogs.sgml @@ -2193,6 +2193,15 @@ SCRAM-SHA-256$<replaceable><iteration count></replaceable>:<replaceable>&l </para></entry> </row> + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>relisivm</structfield> <type>bool</type> + </para> + <para> + True if materialized view enables incremental view maintenance + </para></entry> + </row> + <row> <entry role="catalog_table_entry"><para role="column_definition"> <structfield>relrewrite</structfield> <type>oid</type> @@ -3508,6 +3517,18 @@ SCRAM-SHA-256$<replaceable><iteration count></replaceable>:<replaceable>&l </para> </listitem> </varlistentry> + + <varlistentry> + <term><symbol>DEPENDENCY_IMMV</symbol> (<literal>m</literal>)</term> + <listitem> + <para> + The dependent object was created as part of creation of the Materialized + View with Incremental View Maintenance reference, and is really just a + part of its internal implementation. The dependent object must not be + dropped unless the materialized view is also dropped. + </para> + </listitem> + </varlistentry> </variablelist> Other dependency flavors might be needed in future. @@ -3891,7 +3912,8 @@ SCRAM-SHA-256$<replaceable><iteration count></replaceable>:<replaceable>&l <structfield>extrelocatable</structfield> <type>bool</type> </para> <para> - True if extension can be relocated to another schema + True for materialized views which are enabled for incremental + view maintenance (IVM). </para></entry> </row> diff --git a/doc/src/sgml/ref/create_materialized_view.sgml b/doc/src/sgml/ref/create_materialized_view.sgml index 0d2fea2b97..52a4d206b1 100644 --- a/doc/src/sgml/ref/create_materialized_view.sgml +++ b/doc/src/sgml/ref/create_materialized_view.sgml @@ -21,7 +21,7 @@ PostgreSQL documentation <refsynopsisdiv> <synopsis> -CREATE MATERIALIZED VIEW [ IF NOT EXISTS ] <replaceable>table_name</replaceable> +CREATE [ INCREMENTAL ] MATERIALIZED VIEW [ IF NOT EXISTS ] <replaceable>table_name</replaceable> [ (<replaceable>column_name</replaceable> [, ...] ) ] [ USING <replaceable class="parameter">method</replaceable> ] [ WITH ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] ) ] @@ -60,6 +60,132 @@ CREATE MATERIALIZED VIEW [ IF NOT EXISTS ] <replaceable>table_name</replaceable> <title>Parameters</title> <variablelist> + <varlistentry> + <term><literal>INCREMENTAL</literal></term> + <listitem> + <para> + If specified, some triggers are automatically created so that the rows + of the materialized view are immediately updated when base tables of the + materialized view are updated. In general, this allows faster update of + the materialized view at a price of slower update of the base tables + because the triggers will be invoked. We call this form of materialized + view as "Incrementally Maintainable Materialized View" (IMMV). + </para> + <para> + When <acronym>IMMV</acronym> is defined without using <command>WITH NO DATA</command>, + a unique index is created on the view automatically if possible. If the view + definition query has a GROUP BY clause, a unique index is created on the columns + of GROUP BY expressions. Also, if the view has DISTINCT clause, a unique index + is created on all columns in the target list. Otherwise, if the view contains all + primary key attritubes of its base tables in the target list, a unique index is + created on these attritubes. In other cases, no index is created. + </para> + <para> + There are restrictions of query definitions allowed to use this + option. The following are supported in query definitions for IMMV: + <itemizedlist> + + <listitem> + <para> + Inner joins (including self-joins). + </para> + </listitem> + + <listitem> + <para> + Some built-in aggregate functions (count, sum, avg, min, max) without a HAVING + clause. + </para> + </listitem> + </itemizedlist> + + Unsupported queries with this option include the following: + + <itemizedlist> + <listitem> + <para> + Outer joins. + </para> + </listitem> + + <listitem> + <para> + Sub-queries. + </para> + </listitem> + + <listitem> + <para> + Aggregate functions other than built-in count, sum, avg, min and max. + </para> + </listitem> + <listitem> + <para> + Aggregate functions with a HAVING clause. + </para> + </listitem> + <listitem> + <para> + DISTINCT ON, WINDOW, VALUES, LIMIT and OFFSET clause. + </para> + </listitem> + </itemizedlist> + + Other restrictions include: + <itemizedlist> + + <listitem> + <para> + IMMVs must be based on simple base tables. It's not supported to + create them on top of views or materialized views. + </para> + </listitem> + + <listitem> + <para> + When the TRUNCATE command is executed on a base table, + no changes are made to the materialized view. + </para> + </listitem> + + <listitem> + <para> + It is not supported to include system columns in an IMMV. + <programlisting> +CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm02 AS SELECT i,j FROM mv_base_a WHERE xmin = '610'; +ERROR: system column is not supported with IVM + </programlisting> + </para> + </listitem> + + <listitem> + <para> + Non-immutable functions are not supported. + <programlisting> +CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm12 AS SELECT i,j FROM mv_base_a WHERE i = random()::int; +ERROR: functions in IMMV must be marked IMMUTABLE + </programlisting> + </para> + </listitem> + + <listitem> + <para> + IMMVs do not support expressions that contains aggregates + </para> + </listitem> + + <listitem> + <para> + Logical replication does not support IMMVs. + </para> + </listitem> + + </itemizedlist> + + </para> + </listitem> + </varlistentry> + <varlistentry> <term><literal>IF NOT EXISTS</literal></term> <listitem> @@ -155,7 +281,8 @@ CREATE MATERIALIZED VIEW [ IF NOT EXISTS ] <replaceable>table_name</replaceable> This clause specifies whether or not the materialized view should be populated at creation time. If not, the materialized view will be flagged as unscannable and cannot be queried until <command>REFRESH - MATERIALIZED VIEW</command> is used. + MATERIALIZED VIEW</command> is used. Also, if the view is IMMV, + triggers for maintaining the view are not created. </para> </listitem> </varlistentry> diff --git a/doc/src/sgml/ref/refresh_materialized_view.sgml b/doc/src/sgml/ref/refresh_materialized_view.sgml index 675d6090f3..c29cfc19b6 100644 --- a/doc/src/sgml/ref/refresh_materialized_view.sgml +++ b/doc/src/sgml/ref/refresh_materialized_view.sgml @@ -35,9 +35,13 @@ REFRESH MATERIALIZED VIEW [ CONCURRENTLY ] <replaceable class="parameter">name</ owner of the materialized view. The old contents are discarded. If <literal>WITH DATA</literal> is specified (or defaults) the backing query is executed to provide the new data, and the materialized view is left in a - scannable state. If <literal>WITH NO DATA</literal> is specified no new + scannable state. If the view is an incrementally maintainable materialized + view (IMMV) and was unpopulated, triggers for maintaining the view are + created. Also, a unique index is created for IMMV if it is possible and the + view doesn't have that yet. + If <literal>WITH NO DATA</literal> is specified no new data is generated and the materialized view is left in an unscannable - state. + state. If the view is IMMV, the triggers are dropped. </para> <para> <literal>CONCURRENTLY</literal> and <literal>WITH NO DATA</literal> may not diff --git a/doc/src/sgml/rules.sgml b/doc/src/sgml/rules.sgml index 4b2ba5a4e6..71e10ef5a1 100644 --- a/doc/src/sgml/rules.sgml +++ b/doc/src/sgml/rules.sgml @@ -1090,6 +1090,449 @@ SELECT word FROM words ORDER BY word <-> 'caterpiler' LIMIT 10; </sect1> +<sect1 id="rules-ivm"> +<title>Incremental View Maintenance</title> + +<indexterm zone="rules-ivm"> + <primary>incremental view maintenance</primary> +</indexterm> + +<indexterm zone="rules-ivm"> + <primary>materialized view</primary> + <secondary>incremental view maintenance</secondary> +</indexterm> + +<indexterm zone="rules-ivm"> + <primary>view</primary> + <secondary>incremental view maintenance</secondary> +</indexterm> + +<sect2 id="rules-ivm-overview"> +<title>Overview</title> + +<para> + Incremental View Maintenance (<acronym>IVM</acronym>) is a way to make + materialized views up-to-date in which only incremental changes are computed + and applied on views rather than recomputing the contents from scratch as + <command>REFRESH MATERIALIZED VIEW</command> does. <acronym>IVM</acronym> + can update materialized views more efficiently than recomputation when only + small parts of the view are changed. +</para> + +<para> + There are two approaches with regard to timing of view maintenance: + immediate and deferred. In immediate maintenance, views are updated in the + same transaction that its base table is modified. In deferred maintenance, + views are updated after the transaction is committed, for example, when the + view is accessed, as a response to user command like <command>REFRESH + MATERIALIZED VIEW</command>, or periodically in background, and so on. + <productname>PostgreSQL</productname> currently implements only a kind of + immediate maintenance, in which materialized views are updated immediately + in AFTER triggers when a base table is modified. +</para> + +<para> + To create materialized views supporting <acronym>IVM</acronym>, use the + <command>CREATE INCREMENTAL MATERIALIZED VIEW</command>, for example: +<programlisting> +CREATE <emphasis>INCREMENTAL</emphasis> MATERIALIZED VIEW mymatview AS SELECT * FROM mytab; +</programlisting> + When a materialized view is created with the <literal>INCREMENTAL</literal> + keyword, some triggers are automatically created so that the view's contents are + immediately updated when its base tables are modified. We call this form + of materialized view an Incrementally Maintainable Materialized View + (<acronym>IMMV</acronym>). +<programlisting> +postgres=# CREATE INCREMENTAL MATERIALIZED VIEW m AS SELECT * FROM t0; +NOTICE: could not create an index on materialized view "m" automatically +HINT: Create an index on the materialized view for effcient incremental maintenance. +SELECT 3 +postgres=# SELECT * FROM m; + i +--- + 1 + 2 + 3 +(3 rows) + +postgres=# INSERT INTO t0 VALUES (4); +INSERT 0 1 +postgres=# SELECT * FROM m; -- automatically updated + i +--- + 1 + 2 + 3 + 4 +(4 rows) +</programlisting> +</para> + +<para> + Some <acronym>IMMV</acronym>s have hidden columns which are added + automatically when a materialized view is created. Their name starts + with <literal>__ivm_</literal> and they contain information required + for maintaining the <acronym>IMMV</acronym>. Such columns are not visible + when the <acronym>IMMV</acronym> is accessed by <literal>SELECT *</literal> + but are visible if the column name is explicitly specified in the target + list. We can also see the hidden columns in <literal>\d</literal> + meta-commands of <command>psql</command> commands. +</para> + +<para> + In general, <acronym>IMMV</acronym>s allow faster updates of materialized + views at the price of slower updates to their base tables. Updates of + <acronym>IMMV</acronym> is slower because triggers will be invoked and the + view is updated in triggers per modification statement. +</para> + +<para> + For example, suppose a normal materialized view defined as below: + +<programlisting> +test=# CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm AS + SELECT a.aid, b.bid, a.abalance, b.bbalance + FROM pgbench_accounts a JOIN pgbench_branches b USING(bid); +SELECT 10000000 + +</programlisting> + + Updating a tuple in a base table of this materialized view is rapid but the + <command>REFRESH MATERIALIZED VIEW</command> command on this view takes a long time: + +<programlisting> +test=# UPDATE pgbench_accounts SET abalance = 1000 WHERE aid = 1; +UPDATE 1 +Time: 0.990 ms + +test=# REFRESH MATERIALIZED VIEW mv_normal ; +REFRESH MATERIALIZED VIEW +Time: 33533.952 ms (00:33.534) +</programlisting> +</para> + +<para> + On the other hand, after creating <acronym>IMMV</acronym> with the same view + definition as below: + +<programlisting> +test=# CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm AS + SELECT a.aid, b.bid, a.abalance, b.bbalance + FROM pgbench_accounts a JOIN pgbench_branches b USING(bid); +test=# UPDATE pgbench_accounts SET abalance = 1000 WHERE aid = 1; +NOTICE: created index "mv_ivm_index" on materialized view "mv_ivm" +</programlisting> + + updating a tuple in a base table takes more than the normal view, + but its content is updated automatically and this is faster than the + <command>REFRESH MATERIALIZED VIEW</command> command. + +<programlisting> +test=# UPDATE pgbench_accounts SET abalance = 1000 WHERE aid = 1; +UPDATE 1 +Time: 13.068 ms +</programlisting> + +</para> + +<para> + Appropriate indexes on <acronym>IMMV</acronym>s are necessary for + efficient <acronym>IVM</acronym> because it looks for tuples to be + updated in <acronym>IMMV</acronym>. If there are no indexes, it + will take a long time. +</para> + +<para> + Therefore, when <acronym>IMMV</acronym> is defined, a unique index is created on the view + automatically if possible. If the view definition query has a GROUP BY clause, a unique + index is created on the columns of GROUP BY expressions. Also, if the view has DISTINCT + clause, a unique index is created on all columns in the target list. Otherwise, if the + view contains all primary key attritubes of its base tables in the target list, a unique + index is created on these attritubes. In other cases, no index is created. +</para> + +<para> + In the previous example, a unique index "mv_ivm_index" is created on aid and bid + columns of materialized view "mv_ivm", and this enables the rapid update of the view. + Dropping this index make updating the view take a loger time. +<programlisting> +test=# DROP INDEX mv_ivm_index; +DROP INDEX +Time: 67.081 ms + +test=# UPDATE pgbench_accounts SET abalance = 1000 WHERE aid = 1; +UPDATE 1 +Time: 16386.245 ms (00:16.386) +</programlisting> + +</para> + +<para> + <acronym>IVM</acronym> is effective when we want to keep a materialized + view up-to-date and small fraction of a base table is modified + infrequently. Due to the overhead of immediate maintenance, <acronym>IVM</acronym> + is not effective when a base table is modified frequently. Also, when a + large part of a base table is modified or large data is inserted into a + base table, <acronym>IVM</acronym> is not effective and the cost of + maintenance can be larger than the <command>REFRESH MATERIALIZED VIEW</command> + command. In such situation, we can use <command>REFRESH MATERIALIZED VIEW</command> + and specify <literal>WITH NO DATA</literal> to disable immediate + maintenance before modifying a base table. After a base table modification, + execute the <command>REFRESH MATERIALIZED VIEW</command> (with <literal>WITH DATA</literal>) + command to refresh the view data and enable immediate maintenance. +</para> + +</sect2> + +<sect2> +<title>Supported View Definitions and Restrictions</title> + +<para> + Currently, we can create <acronym>IMMV</acronym>s using inner joins, and some + aggregates. However, several restrictions apply to the definition of IMMV. +</para> + +<sect3> +<title>Joins</title> +<para> + Inner joins including self-join are supported. Outer joins are not supported. +</para> +</sect3> + +<sect3> +<title>Aggregates</title> +<para> + Supported aggregate functions are <function>count</function>, <function>sum</function>, + <function>avg</function>, <function>min</function>, and <function>max</function>. + Currently, only built-in aggregate functions are supported and user defined + aggregates cannot be used. When a base table is modified, the new aggregated + values are incrementally calculated using the old aggregated values and values + of related hidden columns stored in <acronym>IMMV</acronym>. +</para> + +<para> + Note that for <function>min</function> or <function>max</function>, the new values + could be re-calculated from base tables with regard to the affected groups when a + tuple containing the current minimal or maximal values are deleted from a base table. + Therefore, it can takes a long time to update an <acronym>IMMV</acronym> containing + these functions. +</para> + +<para> + Also note that using <function>sum</function> or <function>avg</function> on + <type>real</type> (<type>float4</type>) type or <type>double precision</type> + (<type>float8</type>) type in <acronym>IMMV</acronym> is unsafe. This is + because aggregated values in <acronym>IMMV</acronym> can become different from + results calculated from base tables due to the limited precision of these types. + To avoid this problem, use the <type>numeric</type> type instead. +</para> + + <sect4> + <title>Restrictions on Aggregates</title> + <para> + There are the following restrictions: + <itemizedlist> + <listitem> + <para> + If we have a <literal>GROUP BY</literal> clause, expressions specified in + <literal>GROUP BY</literal> must appear in the target list. This is + how tuples to be updated in the <acronym>IMMV</acronym> are identified. + These attributes are used as scan keys for searching tuples in the + <acronym>IMMV</acronym>, so indexes on them are required for efficient + <acronym>IVM</acronym>. + </para> + </listitem> + + <listitem> + <para> + <literal>HAVING</literal> clause cannot be used. + </para> + </listitem> + </itemizedlist> + </para> + </sect4> +</sect3> + +<sect3> +<title>Other General Restrictions</title> +<para> + There are other restrictions which generally apply to <acronym>IMMV</acronym>: + <itemizedlist> + <listitem> + <para> + Sub-queries cannot be used. + </para> + </listitem> + + <listitem> + <para> + CTEs cannot be used. + </para> + </listitem> + + <listitem> + <para> + Window functions cannot be used. + </para> + </listitem> + + <listitem> + <para> + <acronym>IMMV</acronym>s must be based on simple base tables. It's not + supported to create them on top of views, materialized views, foreign tables, inhe. + </para> + </listitem> + + <listitem> + <para> + LIMIT and OFFSET clauses cannot be used. + </para> + </listitem> + + <listitem> + <para> + <acronym>IMMV</acronym>s cannot contain system columns. + </para> + </listitem> + + <listitem> + <para> + <acronym>IMMV</acronym>s cannot contain non-immutable functions. + </para> + </listitem> + + <listitem> + <para> + UNION/INTERSECT/EXCEPT clauses cannnot be used. + </para> + </listitem> + + <listitem> + <para> + DISTINCT ON clauses cannot be used. + </para> + </listitem> + + <listitem> + <para> + TABLESAMPLE parameter cannot be used. + </para> + </listitem> + + <listitem> + <para> + inheritance parent tables cannnot be used. + </para> + </listitem> + + <listitem> + <para> + VALUES clause cannnot be used. + </para> + </listitem> + + <listitem> + <para> + <literal>GROUPING SETS</literal> and <literal>FILTER</literal> clauses cannot be used. + </para> + </listitem> + + <listitem> + <para> + FOR UPDATE/SHARE cannot be used. + </para> + </listitem> + + <listitem> + <para> + targetlist cannot contain columns whose name start with <literal>__ivm_</literal>. + </para> + </listitem> + + <listitem> + <para> + targetlist cannot contain expressions which contain an aggregate in it. + </para> + </listitem> + + <listitem> + <para> + Logical replication is not supported, that is, even when a base table + at a publisher node is modified, <acronym>IMMV</acronym>s at subscriber + nodes are not updated. + </para> + </listitem> + + <listitem> + <para> + When the <literal>TRUNCATE</literal> command is executed on a base table, + nothing is changed on the <acronym>IMMV</acronym>. + </para> + </listitem> + + </itemizedlist> +</para> +</sect3> + +</sect2> + +<sect2> +<title><literal>DISTINCT</literal></title> + +<para> + <productname>PostgreSQL</productname> supports <acronym>IMMV</acronym> with + <literal>DISTINCT</literal>. For example, suppose a <acronym>IMMV</acronym> + defined with <literal>DISTINCT</literal> on a base table containing duplicate + tuples. When tuples are deleted from the base table, a tuple in the view is + deleted if and only if the multiplicity of the tuple becomes zero. Moreover, + when tuples are inserted into the base table, a tuple is inserted into the + view only if the same tuple doesn't already exist in it. +</para> + +<para> + Physically, an <acronym>IMMV</acronym> defined with <literal>DISTINCT</literal> + contains tuples after eliminating duplicates, and the multiplicity of each tuple + is stored in a hidden column named <literal>__ivm_count__</literal>. +</para> +</sect2> + +<sect2> +<title>Concurrent Transactions</title> +<para> + Suppose an <acronym>IMMV</acronym> is defined on two base tables and each + table was modified in different a concurrent transaction simultaneously. + In the transaction which was committed first, <acronym>IMMV</acronym> can + be updated considering only the change which happened in this transaction. + On the other hand, in order to update the view correctly in the transaction + which was committed later, we need to know the changes occurred in + both transactions. For this reason, <literal>ExclusiveLock</literal> + is held on an <acronym>IMMV</acronym> immediately after a base table is + modified in <literal>READ COMMITTED</literal> mode to make sure that + the <acronym>IMMV</acronym> is updated in the latter transaction after + the former transaction is committed. In <literal>REPEATABLE READ</literal> + or <literal>SERIALIZABLE</literal> mode, an error is raised immediately + if lock acquisition fails because any changes which occurred in + other transactions are not be visible in these modes and + <acronym>IMMV</acronym> cannot be updated correctly in such situations. + However, as an exception if the view has only one base table, + the lock held on thew view is <literal>RowExclusiveLock</literal>. +</para> +</sect2> + +<sect2> +<title>Row Level Security</title> +<para> + If some base tables have row level security policy, rows that are not visible + to the materialized view's owner are excluded from the result. In addition, such + rows are excluded as well when views are incrementally maintained. However, if a + new policy is defined or policies are changed after the materialized view was created, + the new policy will not be applied to the view contents. To apply the new policy, + you need to refresh materialized views. +</para> +</sect2> + +</sect1> + <sect1 id="rules-update"> <title>Rules on <command>INSERT</command>, <command>UPDATE</command>, and <command>DELETE</command></title> -- 2.17.1 --Multipart=_Fri__22_Apr_2022_14_58_01_+0900_MN3L/o2YUVF2g4zw-- ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v32 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Tue_Apr__7_16_38_17_2020_299)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v32-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v40 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..b829167872 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..c337099061 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.4 ----Next_Part(Wed_Nov__4_17_39_10_2020_208)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v40-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v36 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.4 ----Next_Part(Tue_Sep__8_17_55_57_2020_197)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v36-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v41 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..b829167872 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..c337099061 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.4 ----Next_Part(Fri_Nov__6_09_27_56_2020_738)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v41-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v30 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Wed_Apr__1_17_37_23_2020_570)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v30-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v37 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.4 ----Next_Part(Fri_Sep_25_09_27_26_2020_419)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v37-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v43 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..b829167872 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..c337099061 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Dec_11_16_50_03_2020_915)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v43-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v44 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..b829167872 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..c337099061 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Mon_Dec_21_17_16_20_2020_608)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v44-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v38 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..b829167872 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..c337099061 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.4 ----Next_Part(Thu_Oct__1_09_07_22_2020_252)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v38-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v33 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Thu_Apr_30_13_22_05_2020_409)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v33-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v57 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 1d1d5d2f0e..58ad2991a7 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2961,6 +2961,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Thu_Mar_18_16_56_02_2021_947)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v57-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v29 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 150 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 170 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..fb7e23c4cb 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,146 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert (status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Also move parititon lock if needed */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + /* Move lock along with partition for the bucket */ + if (status->curpartition != next_partition) + { + /* + * Lock the next partition then release the current, not in the + * reverse order to avoid concurrent resizing. Partitions are + * locked in the same order with resize() so dead locks won't + * happen. + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..81a929b8d9 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; + int curbucket; + int nbuckets; + dshash_table_item *curitem; + dsa_pointer pnextitem; + int curpartition; + bool exclusive; +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Wed_Apr__1_15_15_11_2020_923)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v29-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v39 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..b829167872 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..c337099061 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.4 ----Next_Part(Tue_Oct__6_10_06_44_2020_382)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v39-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v57 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 1d1d5d2f0e..58ad2991a7 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2961,6 +2961,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Thu_Mar_18_16_56_02_2021_947)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v57-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v33 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Fri_May_15_17_30_36_2020_111)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v33-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v35 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Mon_Jun__8_17_32_04_2020_489)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v35-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v25 2/8] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 162 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 +++++ 2 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..2086bdbea9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -112,6 +112,7 @@ struct dshash_table size_t size_log2; /* log2(number of buckets) */ bool find_locked; /* Is any partition lock held by 'find'? */ bool find_exclusively_locked; /* ... exclusively? */ + bool seqscan_running;/* now under sequential scan */ }; /* Given a pointer to an item, find the entry (user data) it holds. */ @@ -127,6 +128,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +158,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -228,6 +237,7 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg) hash_table->find_locked = false; hash_table->find_exclusively_locked = false; + hash_table->seqscan_running = false; /* * Set up the initial array of buckets. Our initial size is the same as @@ -279,6 +289,7 @@ dshash_attach(dsa_area *area, const dshash_parameters *params, hash_table->control = dsa_get_address(area, control); hash_table->find_locked = false; hash_table->find_exclusively_locked = false; + hash_table->seqscan_running = false; Assert(hash_table->control->magic == DSHASH_MAGIC); /* @@ -324,7 +335,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -568,6 +579,8 @@ dshash_release_lock(dshash_table *hash_table, void *entry) Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition_index), hash_table->find_exclusively_locked ? LW_EXCLUSIVE : LW_SHARED)); + /* lock is under control of sequential scan */ + Assert(!hash_table->seqscan_running); hash_table->find_locked = false; hash_table->find_exclusively_locked = false; @@ -592,6 +605,153 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + /* allowed at most one scan at once */ + Assert(!hash_table->seqscan_running); + + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; + hash_table->seqscan_running = true; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + Assert(status->hash_table->seqscan_running); + if (status->curitem == NULL) + { + int partition; + + Assert (status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Also move parititon lock if needed */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + /* Move lock along with partition for the bucket */ + if (status->curpartition != next_partition) + { + /* + * Lock the next partition then release the current, not in the + * reverse order to avoid concurrent resizing. Partitions are + * locked in the same order with resize() so dead locks won't + * happen. + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + Assert(status->hash_table->seqscan_running); + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + status->hash_table->seqscan_running = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..81a929b8d9 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; + int curbucket; + int nbuckets; + dshash_table_item *curitem; + dsa_pointer pnextitem; + int curpartition; + bool exclusive; +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Thu_Mar_19_20_30_04_2020_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v25-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v31 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Fri_Apr__3_17_31_17_2020_104)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v31-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v34 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 149 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 21 ++++++ 2 files changed, 169 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..1ef093e2e9 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,145 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..0ca9514021 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,12 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.2 ----Next_Part(Mon_Jun__1_18_00_01_2020_089)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v34-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e4d2debb3c..21fd98af66 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_17_51_37_2021_192)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v52-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Wed_Mar_10_12_10_39_2021_432)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v51-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v42 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index 78ccf03217..b829167872 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index b86df68e77..c337099061 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.18.4 ----Next_Part(Wed_Nov_11_10_07_22_2020_796)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v42-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_16_53_11_2021_575)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v49-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_21_12_03_48_2021_284)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v47-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Thu_Jan_14_15_14_25_2021_903)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v46-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This commit adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan is in progress. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 161 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 183 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..29ad767618 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,157 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition PG_USED_FOR_ASSERTS_ONLY + = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 61cf4eae1f..78e852569e 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2958,6 +2958,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar_16_10_27_55_2021_500)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v56-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 ++++++ 2 files changed, 181 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); -- 2.27.0 ----Next_Part(Fri_Jan__8_10_24_34_2021_185)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v45-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Tue_Mar__9_18_29_34_2021_806)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v50-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 230+ messages in thread From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw) Dshash did not allow scan the all entries sequentially. This adds the functionality. The interface is similar but a bit different both from that of dynahash and simple dshash search functions. One of the most significant differences is the sequential scan interface of dshash always needs a call to dshash_seq_term when scan ends. Another is locking. Dshash holds partition lock when returning an entry, dshash_seq_next() also holds lock when returning an entry but callers shouldn't release it, since the lock is essential to continue a scan. The seqscan interface allows entry deletion while a scan. The in-scan deletion should be performed by dshash_delete_current(). --- src/backend/lib/dshash.c | 160 ++++++++++++++++++++++++++++++- src/include/lib/dshash.h | 22 +++++ src/tools/pgindent/typedefs.list | 1 + 3 files changed, 182 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index e0c763be32..520bfa0979 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -127,6 +127,10 @@ struct dshash_table #define NUM_SPLITS(size_log2) \ (size_log2 - DSHASH_NUM_PARTITIONS_LOG2) +/* How many buckets are there in a given size? */ +#define NUM_BUCKETS(size_log2) \ + (((size_t) 1) << (size_log2)) + /* How many buckets are there in each partition at a given size? */ #define BUCKETS_PER_PARTITION(size_log2) \ (((size_t) 1) << NUM_SPLITS(size_log2)) @@ -153,6 +157,10 @@ struct dshash_table #define BUCKET_INDEX_FOR_PARTITION(partition, size_log2) \ ((partition) << NUM_SPLITS(size_log2)) +/* Choose partition based on bucket index. */ +#define PARTITION_FOR_BUCKET_INDEX(bucket_idx, size_log2) \ + ((bucket_idx) >> NUM_SPLITS(size_log2)) + /* The head of the active bucket for a given hash value (lvalue). */ #define BUCKET_FOR_HASH(hash_table, hash) \ (hash_table->buckets[ \ @@ -324,7 +332,7 @@ dshash_destroy(dshash_table *hash_table) ensure_valid_bucket_pointers(hash_table); /* Free all the entries. */ - size = ((size_t) 1) << hash_table->size_log2; + size = NUM_BUCKETS(hash_table->size_log2); for (i = 0; i < size; ++i) { dsa_pointer item_pointer = hash_table->buckets[i]; @@ -592,6 +600,156 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * dshash_seq_init/_next/_term + * Sequentially scan through dshash table and return all the + * elements one by one, return NULL when no more. + * + * dshash_seq_term should always be called when a scan finished. + * The caller may delete returned elements midst of a scan by using + * dshash_delete_current(). exclusive must be true to delete elements. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = 0; + status->curitem = NULL; + status->pnextitem = InvalidDsaPointer; + status->curpartition = -1; + status->exclusive = exclusive; +} + +/* + * Returns the next element. + * + * Returned elements are locked and the caller must not explicitly release + * it. It is released at the next call to dshash_next(). + */ +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + int partition; + + Assert(status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + LWLockAcquire(PARTITION_LOCK(status->hash_table, partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + status->curpartition = partition; + + /* resize doesn't happen from now until seq scan ends */ + status->nbuckets = + NUM_BUCKETS(status->hash_table->control->size_log2); + ensure_valid_bucket_pointers(status->hash_table); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + else + next_item_pointer = status->pnextitem; + + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(status->hash_table, + status->curpartition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED)); + + /* Move to the next bucket if we finished the current bucket */ + while (!DsaPointerIsValid(next_item_pointer)) + { + int next_partition; + + if (++status->curbucket >= status->nbuckets) + { + /* all buckets have been scanned. finish. */ + return NULL; + } + + /* Check if move to the next partition */ + next_partition = + PARTITION_FOR_BUCKET_INDEX(status->curbucket, + status->hash_table->size_log2); + + if (status->curpartition != next_partition) + { + /* + * Move to the next partition. Lock the next partition then release + * the current, not in the reverse order to avoid concurrent + * resizing. Avoid dead lock by taking lock in the same order + * with resize(). + */ + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + status->exclusive ? LW_EXCLUSIVE : LW_SHARED); + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + status->curpartition = next_partition; + } + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + status->hash_table->find_locked = true; + status->hash_table->find_exclusively_locked = status->exclusive; + + /* + * The caller may delete the item. Store the next item in case of deletion. + */ + status->pnextitem = status->curitem->next; + + return ENTRY_FROM_ITEM(status->curitem); +} + +/* + * Terminates the seqscan and release all locks. + * + * Should be always called when finishing or exiting a seqscan. + */ +void +dshash_seq_term(dshash_seq_status *status) +{ + status->hash_table->find_locked = false; + status->hash_table->find_exclusively_locked = false; + + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, status->curpartition)); +} + +/* Remove the current entry while a seq scan. */ +void +dshash_delete_current(dshash_seq_status *status) +{ + dshash_table *hash_table = status->hash_table; + dshash_table_item *item = status->curitem; + size_t partition = PARTITION_FOR_HASH(item->hash); + + Assert(status->exclusive); + Assert(hash_table->control->magic == DSHASH_MAGIC); + Assert(hash_table->find_locked); + Assert(hash_table->find_exclusively_locked); + Assert(LWLockHeldByMeInMode(PARTITION_LOCK(hash_table, partition), + LW_EXCLUSIVE)); + + delete_item(hash_table, item); +} + +/* Get the current entry while a seq scan. */ +void * +dshash_get_current(dshash_seq_status *status) +{ + return ENTRY_FROM_ITEM(status->curitem); +} + /* * Print debugging information about the internal state of the hash table to * stderr. The caller must hold no partition locks. diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h index c069ec9de7..a6ea377173 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -59,6 +59,21 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -80,6 +95,13 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key); extern void dshash_delete_entry(dshash_table *hash_table, void *entry); extern void dshash_release_lock(dshash_table *hash_table, void *entry); +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); +extern void *dshash_get_current(dshash_seq_status *status); /* Convenience hash and compare functions wrapping memcmp and tag_hash. */ extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg); extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg); diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 8bd95aefa1..2b591e94e6 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2954,6 +2954,7 @@ dshash_hash dshash_hash_function dshash_parameters dshash_partition +dshash_seq_status dshash_table dshash_table_control dshash_table_handle -- 2.27.0 ----Next_Part(Fri_Mar__5_17_18_56_2021_497)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v48-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 230+ messages in thread
end of thread, other threads:[~2020-03-13 07:58 UTC | newest] Thread overview: 230+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH v24 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2019-12-20 01:25 [PATCH v27 9/9] Add documentations about Incremental View Maintenance Yugo Nagata <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v56 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v56 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v32 2/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v40 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro 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dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v56 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v56 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v33 2/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v35 2/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v56 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v56 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v25 2/8] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v31 2/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v34 2/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v52 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v51 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v42 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v49 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v47 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v46 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v56 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v45 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v50 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v48 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]>
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