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[PATCH 1/8] sequential scan for dshash 54+ messages / 3 participants [nested] [flat]
* [PATCH 1/8] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 b2b8fe60e1..af904c034e 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 8c733bfe25..8ab1a21f3e 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); -- 2.16.3 ----Next_Part(Thu_Nov_08_20_46_48_2018_519)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v7-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/8] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 | 138 +++++++++++++++++++++++++++++++++++++++++++++++ src/include/lib/dshash.h | 23 +++++++- 2 files changed, 160 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index b46f7c4cfd..5b133226ac 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -592,6 +592,144 @@ 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) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = ((size_t) 1) << hash_table->control->size_log2; + status->curitem = NULL; + status->curpartition = -1; + status->consistent = consistent; + + /* + * 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), LW_SHARED); + } + } + ensure_valid_bucket_pointers(hash_table); +} + +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + Assert (status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + next_item_pointer = status->hash_table->buckets[status->curbucket]; + status->hash_table->find_locked = true; + } + else + next_item_pointer = status->curitem->next; + + /* 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; + } + Assert(status->hash_table->find_locked); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + + /* + * we need a lock on the scanning partition even if the caller don't + * requested a consistent snapshot. + */ + if (!status->consistent && DsaPointerIsValid(next_item_pointer)) + { + dshash_table_item *item = dsa_get_address(status->hash_table->area, + next_item_pointer); + int next_partition = PARTITION_FOR_HASH(item->hash); + if (status->curpartition != next_partition) + { + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + LW_SHARED); + status->curpartition = next_partition; + } + } + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + return ENTRY_FROM_ITEM(status->curitem); +} + +void +dshash_seq_term(dshash_seq_status *status) +{ + Assert(status->hash_table->find_locked); + status->hash_table->find_locked = 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)); +} + +int +dshash_get_num_entries(dshash_table *hash_table) +{ + /* a shotcut implement. should be improved */ + dshash_seq_status s; + void *p; + int n = 0; + + dshash_seq_init(&s, hash_table, false); + while ((p = dshash_seq_next(&s)) != NULL) + n++; + + return n; +} + /* * 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 8c733bfe25..8598d9ed84 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -15,6 +15,7 @@ #define DSHASH_H #include "utils/dsa.h" +#include "utils/hsearch.h" /* The opaque type representing a hash table. */ struct dshash_table; @@ -59,6 +60,21 @@ 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; + int curpartition; + bool consistent; +} 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 +95,12 @@ 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 int dshash_get_num_entries(dshash_table *hash_table); /* 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); -- 2.16.3 ----Next_Part(Thu_Sep_27_22_00_49_2018_853)---- ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/7] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 b2b8fe60e1..af904c034e 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 8c733bfe25..8ab1a21f3e 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); -- 2.16.3 ----Next_Part(Tue_Nov_27_17_59_49_2018_846)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v10-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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); -- 2.16.3 ----Next_Part(Thu_Jul_11_16_40_59_2019_397)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v21-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..d1908a6137 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Mon_Feb_18_21_35_31_2019_949)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v14-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..d1908a6137 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Tue_Feb_19_21_40_07_2019_247)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v15-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH v24 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH 1/3] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 | 122 +++++++++++++++++++++++++++++++++++++++++++++++ src/include/lib/dshash.h | 20 +++++++- 2 files changed, 141 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index b46f7c4cfd..e6c1ef44f1 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -592,6 +592,128 @@ dshash_memhash(const void *v, size_t size, void *arg) return tag_hash(v, size); } +/* + * Initialize a sequential scan on the hash_table. Allows no modifications + * during a scan if consistent = true. + */ +void +dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool consistent) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = ((size_t) 1) << hash_table->control->size_log2; + status->curitem = NULL; + status->curpartition = -1; + status->consistent = consistent; + + /* + * 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), LW_SHARED); + } + } + ensure_valid_bucket_pointers(hash_table); +} + +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + Assert (status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + next_item_pointer = status->hash_table->buckets[status->curbucket]; + status->hash_table->find_locked = true; + } + else + next_item_pointer = status->curitem->next; + + /* 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_release(status); + return NULL; + } + Assert(status->hash_table->find_locked); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + + /* + * we need a lock on the scanning partition even if the caller don't + * requested a consistent snapshot. + */ + if (!status->consistent && DsaPointerIsValid(next_item_pointer)) + { + dshash_table_item *item = dsa_get_address(status->hash_table->area, + next_item_pointer); + int next_partition = PARTITION_FOR_HASH(item->hash); + if (status->curpartition != next_partition) + { + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + LW_SHARED); + status->curpartition = next_partition; + } + } + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + return ENTRY_FROM_ITEM(status->curitem); +} + +void +dshash_seq_release(dshash_seq_status *status) +{ + Assert(status->hash_table->find_locked); + status->hash_table->find_locked = 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)); +} + +int +dshash_get_num_entries(dshash_table *hash_table) +{ + /* a shotcut implement. should be improved */ + dshash_seq_status s; + void *p; + int n = 0; + + dshash_seq_init(&s, hash_table, false); + while ((p = dshash_seq_next(&s)) != NULL) + n++; + + return n; +} + /* * 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 8c733bfe25..a4565d3219 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -15,6 +15,7 @@ #define DSHASH_H #include "utils/dsa.h" +#include "utils/hsearch.h" /* The opaque type representing a hash table. */ struct dshash_table; @@ -59,6 +60,18 @@ typedef struct dshash_parameters struct dshash_table_item; typedef struct dshash_table_item dshash_table_item; +struct dshash_seq_status +{ + dshash_table *hash_table; + int curbucket; + int nbuckets; + dshash_table_item *curitem; + int curpartition; + bool consistent; +}; + +typedef struct dshash_seq_status dshash_seq_status; + /* Creating, sharing and destroying from hash tables. */ extern dshash_table *dshash_create(dsa_area *area, const dshash_parameters *params, @@ -70,7 +83,6 @@ 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 +92,12 @@ 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_release(dshash_seq_status *status); +extern int dshash_get_num_entries(dshash_table *hash_table); /* 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); -- 2.16.3 ----Next_Part(Tue_Jul_03_19_01_44_2018_430)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v2-0002-Change-stats-collector-to-an-axiliary-process.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/6] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 | 138 +++++++++++++++++++++++++++++++++++++++++++++++ src/include/lib/dshash.h | 23 +++++++- 2 files changed, 160 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index b46f7c4cfd..5b133226ac 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -592,6 +592,144 @@ 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) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = ((size_t) 1) << hash_table->control->size_log2; + status->curitem = NULL; + status->curpartition = -1; + status->consistent = consistent; + + /* + * 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), LW_SHARED); + } + } + ensure_valid_bucket_pointers(hash_table); +} + +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + Assert (status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + next_item_pointer = status->hash_table->buckets[status->curbucket]; + status->hash_table->find_locked = true; + } + else + next_item_pointer = status->curitem->next; + + /* 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; + } + Assert(status->hash_table->find_locked); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + + /* + * we need a lock on the scanning partition even if the caller don't + * requested a consistent snapshot. + */ + if (!status->consistent && DsaPointerIsValid(next_item_pointer)) + { + dshash_table_item *item = dsa_get_address(status->hash_table->area, + next_item_pointer); + int next_partition = PARTITION_FOR_HASH(item->hash); + if (status->curpartition != next_partition) + { + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + LW_SHARED); + status->curpartition = next_partition; + } + } + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + return ENTRY_FROM_ITEM(status->curitem); +} + +void +dshash_seq_term(dshash_seq_status *status) +{ + Assert(status->hash_table->find_locked); + status->hash_table->find_locked = 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)); +} + +int +dshash_get_num_entries(dshash_table *hash_table) +{ + /* a shotcut implement. should be improved */ + dshash_seq_status s; + void *p; + int n = 0; + + dshash_seq_init(&s, hash_table, false); + while ((p = dshash_seq_next(&s)) != NULL) + n++; + + return n; +} + /* * 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 8c733bfe25..8598d9ed84 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -15,6 +15,7 @@ #define DSHASH_H #include "utils/dsa.h" +#include "utils/hsearch.h" /* The opaque type representing a hash table. */ struct dshash_table; @@ -59,6 +60,21 @@ 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; + int curpartition; + bool consistent; +} 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 +95,12 @@ 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 int dshash_get_num_entries(dshash_table *hash_table); /* 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); -- 2.16.3 ----Next_Part(Wed_Jul_04_17_29_11_2018_498)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v3-0002-Change-stats-collector-to-an-axiliary-process.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 24dd372252..a0ccd7ee7c 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); -- 2.16.3 ----Next_Part(Thu_Jul_04_19_27_54_2019_888)-- 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] 54+ messages in thread
* [PATCH 1/6] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..1e8c22f94f 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Thu_Feb_21_16_05_55_2019_560)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v16-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/6] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..1e8c22f94f 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Mon_Feb_25_13_52_14_2019_191)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v17-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/9] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 b2b8fe60e1..af904c034e 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 8c733bfe25..8ab1a21f3e 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); -- 2.16.3 ----Next_Part(Fri_Nov_09_17_33_15_2018_162)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v8-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH v22 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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); -- 2.16.3 ----Next_Part(Tue_Sep_10_17_58_58_2019_765)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v22-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH v23 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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); -- 2.16.3 ----Next_Part(Fri_Sep_27_09_46_47_2019_292)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v23-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..1e8c22f94f 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Fri_May_17_14_27_22_2019_078)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v19-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..1e8c22f94f 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Fri_May_17_15_47_20_2019_554)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v20-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/7] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..d1908a6137 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Mon_Jan_21_21_19_07_2019_726)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v11-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..d1908a6137 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Tue_Jan_22_15_48_02_2019_276)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v12-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..d1908a6137 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Fri_Feb_15_17_29_00_2019_199)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v13-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/5] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 f095196fb6..1e8c22f94f 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 e5dfd57f0a..b80f3af995 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); -- 2.16.3 ----Next_Part(Wed_Mar_27_16_36_25_2019_836)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v18-0002-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/6] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 | 138 +++++++++++++++++++++++++++++++++++++++++++++++ src/include/lib/dshash.h | 23 +++++++- 2 files changed, 160 insertions(+), 1 deletion(-) diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c index b46f7c4cfd..5b133226ac 100644 --- a/src/backend/lib/dshash.c +++ b/src/backend/lib/dshash.c @@ -592,6 +592,144 @@ 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) +{ + status->hash_table = hash_table; + status->curbucket = 0; + status->nbuckets = ((size_t) 1) << hash_table->control->size_log2; + status->curitem = NULL; + status->curpartition = -1; + status->consistent = consistent; + + /* + * 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), LW_SHARED); + } + } + ensure_valid_bucket_pointers(hash_table); +} + +void * +dshash_seq_next(dshash_seq_status *status) +{ + dsa_pointer next_item_pointer; + + if (status->curitem == NULL) + { + Assert (status->curbucket == 0); + Assert(!status->hash_table->find_locked); + + /* first shot. grab the first item. */ + next_item_pointer = status->hash_table->buckets[status->curbucket]; + status->hash_table->find_locked = true; + } + else + next_item_pointer = status->curitem->next; + + /* 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; + } + Assert(status->hash_table->find_locked); + + next_item_pointer = status->hash_table->buckets[status->curbucket]; + + /* + * we need a lock on the scanning partition even if the caller don't + * requested a consistent snapshot. + */ + if (!status->consistent && DsaPointerIsValid(next_item_pointer)) + { + dshash_table_item *item = dsa_get_address(status->hash_table->area, + next_item_pointer); + int next_partition = PARTITION_FOR_HASH(item->hash); + if (status->curpartition != next_partition) + { + if (status->curpartition >= 0) + LWLockRelease(PARTITION_LOCK(status->hash_table, + status->curpartition)); + LWLockAcquire(PARTITION_LOCK(status->hash_table, + next_partition), + LW_SHARED); + status->curpartition = next_partition; + } + } + } + + status->curitem = + dsa_get_address(status->hash_table->area, next_item_pointer); + return ENTRY_FROM_ITEM(status->curitem); +} + +void +dshash_seq_term(dshash_seq_status *status) +{ + Assert(status->hash_table->find_locked); + status->hash_table->find_locked = 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)); +} + +int +dshash_get_num_entries(dshash_table *hash_table) +{ + /* a shotcut implement. should be improved */ + dshash_seq_status s; + void *p; + int n = 0; + + dshash_seq_init(&s, hash_table, false); + while ((p = dshash_seq_next(&s)) != NULL) + n++; + + return n; +} + /* * 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 8c733bfe25..8598d9ed84 100644 --- a/src/include/lib/dshash.h +++ b/src/include/lib/dshash.h @@ -15,6 +15,7 @@ #define DSHASH_H #include "utils/dsa.h" +#include "utils/hsearch.h" /* The opaque type representing a hash table. */ struct dshash_table; @@ -59,6 +60,21 @@ 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; + int curpartition; + bool consistent; +} 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 +95,12 @@ 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 int dshash_get_num_entries(dshash_table *hash_table); /* 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); -- 2.16.3 ----Next_Part(Tue_Jul_10_21_07_40_2018_417)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v4-0002-Change-stats-collector-to-an-axiliary-process.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH 1/7] sequential scan for dshash @ 2018-06-29 07:41 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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 b2b8fe60e1..af904c034e 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 8c733bfe25..8ab1a21f3e 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); -- 2.16.3 ----Next_Part(Mon_Nov_12_20_10_42_2018_878)---- ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH v29 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v30 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v33 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v25 2/8] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v27 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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(Fri_Mar_27_16_31_15_2020_716)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v27-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH v50 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v51 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v52 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v57 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v44 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v37 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v33 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v32 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v28 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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(Mon_Mar_30_09_29_45_2020_582)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v28-0003-Add-conditional-lock-feature-to-dshash.patch" ^ permalink raw reply [nested|flat] 54+ messages in thread
* [PATCH v39 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v31 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v56 1/6] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v40 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v35 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v41 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v45 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v46 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v47 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v49 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v48 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v43 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v38 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v42 1/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v34 2/7] sequential scan for dshash @ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 54+ 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] 54+ messages in thread
* [PATCH v2] Avoid orphaned objects dependencies @ 2024-03-29 15:43 Bertrand Drouvot <[email protected]> 0 siblings, 0 replies; 54+ messages in thread From: Bertrand Drouvot @ 2024-03-29 15:43 UTC (permalink / raw) It's currently possible to create orphaned objects dependencies, for example: Scenario 1: session 1: begin; drop schema schem; session 2: create a function in the schema schem session 1: commit; With the above, the function created in session 2 would be linked to a non existing schema. Scenario 2: session 1: begin; create a function in the schema schem session 2: drop schema schem; session 1: commit; With the above, the function created in session 1 would be linked to a non existing schema. To avoid those scenarios, a new lock (that conflicts with a lock taken by DROP) has been put in place when the dependencies are being recorded. With this in place, the drop schema in scenario 2 would be locked. Also, after locking the object, the patch checks that the object still exists: with this in place session 2 in scenario 1 would be locked and would report an error once session 1 committs (that would not be the case should session 1 abort the transaction). The patch adds a few tests for some dependency cases (that would currently produce orphaned objects): - schema and function (as the above scenarios) - function and type - table and type --- src/backend/catalog/dependency.c | 48 +++++++++++++ src/backend/catalog/objectaddress.c | 70 +++++++++++++++++++ src/backend/catalog/pg_depend.c | 6 ++ src/include/catalog/dependency.h | 1 + src/include/catalog/objectaddress.h | 1 + src/test/modules/Makefile | 1 + src/test/modules/meson.build | 1 + .../test_dependencies_locks/.gitignore | 3 + .../modules/test_dependencies_locks/Makefile | 14 ++++ .../expected/test_dependencies_locks.out | 49 +++++++++++++ .../test_dependencies_locks/meson.build | 12 ++++ .../specs/test_dependencies_locks.spec | 39 +++++++++++ 12 files changed, 245 insertions(+) 38.1% src/backend/catalog/ 30.7% src/test/modules/test_dependencies_locks/expected/ 19.5% src/test/modules/test_dependencies_locks/specs/ 8.7% src/test/modules/test_dependencies_locks/ diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c index d4b5b2ade1..e3b66025dd 100644 --- a/src/backend/catalog/dependency.c +++ b/src/backend/catalog/dependency.c @@ -1517,6 +1517,54 @@ AcquireDeletionLock(const ObjectAddress *object, int flags) } } +/* + * depLockAndCheckObject + * + * Lock the object that we are about to record a dependency on. + * After it's locked, verify that it hasn't been dropped while we + * weren't looking. If the object has been dropped, this function + * does not return! + */ +void +depLockAndCheckObject(const ObjectAddress *object) +{ + char *object_description; + + /* + * Those don't rely on LockDatabaseObject() when being dropped (see + * AcquireDeletionLock()). Also it looks like they can not produce + * orphaned dependent objects when being dropped. + */ + if (object->classId == RelationRelationId || object->classId == AuthMemRelationId) + return; + + object_description = getObjectDescription(object, true); + + /* assume we should lock the whole object not a sub-object */ + LockDatabaseObject(object->classId, object->objectId, 0, AccessShareLock); + + /* check if object still exists */ + if (!ObjectByIdExist(object, false)) + { + /* + * It might be possible that we are creating it, so bypass the syscache + * lookup and use a dirty snaphot instead. + */ + if (!ObjectByIdExist(object, true)) + { + if(object_description) + ereport(ERROR, errmsg("%s does not exist", object_description)); + else + ereport(ERROR, errmsg("a dependent object does not exist")); + } + } + + if (object_description) + pfree(object_description); + + return; +} + /* * ReleaseDeletionLock - release an object deletion lock * diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c index 7b536ac6fd..c2b873dd81 100644 --- a/src/backend/catalog/objectaddress.c +++ b/src/backend/catalog/objectaddress.c @@ -2590,6 +2590,76 @@ get_object_namespace(const ObjectAddress *address) return oid; } +/* + * ObjectByIdExist + * + * Return whether the given object exists. + * + * Works for most catalogs, if no special processing is needed. + */ +bool +ObjectByIdExist(const ObjectAddress *address, bool use_dirty_snapshot) +{ + HeapTuple tuple; + int cache = -1; + const ObjectPropertyType *property; + + if (!use_dirty_snapshot) + { + property = get_object_property_data(address->classId); + + cache = property->oid_catcache_id; + } + + if (cache >= 0) + { + /* Fetch tuple from syscache. */ + tuple = SearchSysCache1(cache, ObjectIdGetDatum(address->objectId)); + + if (!HeapTupleIsValid(tuple)) + { + return false; + } + + ReleaseSysCache(tuple); + + return true; + } + else + { + Relation rel; + ScanKeyData skey[1]; + SysScanDesc scan; + SnapshotData DirtySnapshot; + Snapshot snapshot; + + if (use_dirty_snapshot) + { + InitDirtySnapshot(DirtySnapshot); + snapshot = &DirtySnapshot; + } + else + snapshot = NULL; + + rel = table_open(address->classId, AccessShareLock); + + ScanKeyInit(&skey[0], + get_object_attnum_oid(address->classId), + BTEqualStrategyNumber, F_OIDEQ, + ObjectIdGetDatum(address->objectId)); + + scan = systable_beginscan(rel, get_object_oid_index(address->classId), true, + snapshot, 1, skey); + + /* we expect exactly one match */ + tuple = systable_getnext(scan); + systable_endscan(scan); + table_close(rel, AccessShareLock); + + return (HeapTupleIsValid(tuple)); + } +} + /* * Return ObjectType for the given object type as given by * getObjectTypeDescription; if no valid ObjectType code exists, but it's a diff --git a/src/backend/catalog/pg_depend.c b/src/backend/catalog/pg_depend.c index f85a898de8..6bb218f5dd 100644 --- a/src/backend/catalog/pg_depend.c +++ b/src/backend/catalog/pg_depend.c @@ -106,6 +106,12 @@ recordMultipleDependencies(const ObjectAddress *depender, if (isObjectPinned(referenced)) continue; + /* + * Acquire a lock and check object still exists while recording the + * dependency. XXX - Should we do so only for DEPENDENCY_NORMAL? + */ + depLockAndCheckObject(referenced); + if (slot_init_count < max_slots) { slot[slot_stored_count] = MakeSingleTupleTableSlot(RelationGetDescr(dependDesc), diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h index ec654010d4..8915548711 100644 --- a/src/include/catalog/dependency.h +++ b/src/include/catalog/dependency.h @@ -94,6 +94,7 @@ typedef struct ObjectAddresses ObjectAddresses; /* in dependency.c */ extern void AcquireDeletionLock(const ObjectAddress *object, int flags); +extern void depLockAndCheckObject(const ObjectAddress *object); extern void ReleaseDeletionLock(const ObjectAddress *object); diff --git a/src/include/catalog/objectaddress.h b/src/include/catalog/objectaddress.h index 3a70d80e32..04891abcc1 100644 --- a/src/include/catalog/objectaddress.h +++ b/src/include/catalog/objectaddress.h @@ -53,6 +53,7 @@ extern void check_object_ownership(Oid roleid, Node *object, Relation relation); extern Oid get_object_namespace(const ObjectAddress *address); +extern bool ObjectByIdExist(const ObjectAddress *address, bool use_dirty_snapshot); extern bool is_objectclass_supported(Oid class_id); extern const char *get_object_class_descr(Oid class_id); diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile index 256799f520..75f357100f 100644 --- a/src/test/modules/Makefile +++ b/src/test/modules/Makefile @@ -17,6 +17,7 @@ SUBDIRS = \ test_copy_callbacks \ test_custom_rmgrs \ test_ddl_deparse \ + test_dependencies_locks \ test_dsa \ test_dsm_registry \ test_extensions \ diff --git a/src/test/modules/meson.build b/src/test/modules/meson.build index d8fe059d23..60305dcccd 100644 --- a/src/test/modules/meson.build +++ b/src/test/modules/meson.build @@ -16,6 +16,7 @@ subdir('test_bloomfilter') subdir('test_copy_callbacks') subdir('test_custom_rmgrs') subdir('test_ddl_deparse') +subdir('test_dependencies_locks') subdir('test_dsa') subdir('test_dsm_registry') subdir('test_extensions') diff --git a/src/test/modules/test_dependencies_locks/.gitignore b/src/test/modules/test_dependencies_locks/.gitignore new file mode 100644 index 0000000000..bf000faac4 --- /dev/null +++ b/src/test/modules/test_dependencies_locks/.gitignore @@ -0,0 +1,3 @@ +# Generated subdirectories +/log/ +/output_iso diff --git a/src/test/modules/test_dependencies_locks/Makefile b/src/test/modules/test_dependencies_locks/Makefile new file mode 100644 index 0000000000..7491048380 --- /dev/null +++ b/src/test/modules/test_dependencies_locks/Makefile @@ -0,0 +1,14 @@ +# src/test/modules/test_dependencies_locks/Makefile + +ISOLATION = test_dependencies_locks + +ifdef USE_PGXS +PG_CONFIG = pg_config +PGXS := $(shell $(PG_CONFIG) --pgxs) +include $(PGXS) +else +subdir = src/test/modules/test_dependencies_locks +top_builddir = ../../../.. +include $(top_builddir)/src/Makefile.global +include $(top_srcdir)/contrib/contrib-global.mk +endif diff --git a/src/test/modules/test_dependencies_locks/expected/test_dependencies_locks.out b/src/test/modules/test_dependencies_locks/expected/test_dependencies_locks.out new file mode 100644 index 0000000000..d0980f77d5 --- /dev/null +++ b/src/test/modules/test_dependencies_locks/expected/test_dependencies_locks.out @@ -0,0 +1,49 @@ +Parsed test spec with 2 sessions + +starting permutation: s1_begin s1_create_function_in_schema s2_drop_schema s1_commit +step s1_begin: BEGIN; +step s1_create_function_in_schema: CREATE FUNCTION testschema.foo() RETURNS int AS 'select 1' LANGUAGE sql; +step s2_drop_schema: DROP SCHEMA testschema; <waiting ...> +step s1_commit: COMMIT; +step s2_drop_schema: <... completed> +ERROR: cannot drop schema testschema because other objects depend on it + +starting permutation: s2_begin s2_drop_schema s1_create_function_in_schema s2_commit +step s2_begin: BEGIN; +step s2_drop_schema: DROP SCHEMA testschema; +step s1_create_function_in_schema: CREATE FUNCTION testschema.foo() RETURNS int AS 'select 1' LANGUAGE sql; <waiting ...> +step s2_commit: COMMIT; +step s1_create_function_in_schema: <... completed> +ERROR: schema testschema does not exist + +starting permutation: s1_begin s1_create_function_with_type s2_drop_foo_type s1_commit +step s1_begin: BEGIN; +step s1_create_function_with_type: CREATE FUNCTION footype(num foo) RETURNS int AS 'select 1' LANGUAGE sql; +step s2_drop_foo_type: DROP TYPE public.foo; <waiting ...> +step s1_commit: COMMIT; +step s2_drop_foo_type: <... completed> +ERROR: cannot drop type foo because other objects depend on it + +starting permutation: s2_begin s2_drop_foo_type s1_create_function_with_type s2_commit +step s2_begin: BEGIN; +step s2_drop_foo_type: DROP TYPE public.foo; +step s1_create_function_with_type: CREATE FUNCTION footype(num foo) RETURNS int AS 'select 1' LANGUAGE sql; <waiting ...> +step s2_commit: COMMIT; +step s1_create_function_with_type: <... completed> +ERROR: type foo does not exist + +starting permutation: s1_begin s1_create_table_with_type s2_drop_footab_type s1_commit +step s1_begin: BEGIN; +step s1_create_table_with_type: CREATE TABLE tabtype(a footab); +step s2_drop_footab_type: DROP TYPE public.footab; <waiting ...> +step s1_commit: COMMIT; +step s2_drop_footab_type: <... completed> +ERROR: cannot drop type footab because other objects depend on it + +starting permutation: s2_begin s2_drop_footab_type s1_create_table_with_type s2_commit +step s2_begin: BEGIN; +step s2_drop_footab_type: DROP TYPE public.footab; +step s1_create_table_with_type: CREATE TABLE tabtype(a footab); <waiting ...> +step s2_commit: COMMIT; +step s1_create_table_with_type: <... completed> +ERROR: type footab does not exist diff --git a/src/test/modules/test_dependencies_locks/meson.build b/src/test/modules/test_dependencies_locks/meson.build new file mode 100644 index 0000000000..92a978ab93 --- /dev/null +++ b/src/test/modules/test_dependencies_locks/meson.build @@ -0,0 +1,12 @@ +# Copyright (c) 2024, PostgreSQL Global Development Group + +tests += { + 'name': 'test_dependencies_locks', + 'sd': meson.current_source_dir(), + 'bd': meson.current_build_dir(), + 'isolation': { + 'specs': [ + 'test_dependencies_locks', + ], + }, +} diff --git a/src/test/modules/test_dependencies_locks/specs/test_dependencies_locks.spec b/src/test/modules/test_dependencies_locks/specs/test_dependencies_locks.spec new file mode 100644 index 0000000000..fd15bd2a78 --- /dev/null +++ b/src/test/modules/test_dependencies_locks/specs/test_dependencies_locks.spec @@ -0,0 +1,39 @@ +setup +{ + CREATE SCHEMA testschema; + CREATE TYPE public.foo as enum ('one', 'two'); + CREATE TYPE public.footab as enum ('three', 'four'); +} + +teardown +{ + DROP FUNCTION IF EXISTS testschema.foo(); + DROP FUNCTION IF EXISTS footype(num foo); + DROP TABLE IF EXISTS tabtype; + DROP SCHEMA IF EXISTS testschema; + DROP TYPE IF EXISTS public.foo; + DROP TYPE IF EXISTS public.footab; +} + +session "s1" + +step "s1_begin" { BEGIN; } +step "s1_create_function_in_schema" { CREATE FUNCTION testschema.foo() RETURNS int AS 'select 1' LANGUAGE sql; } +step "s1_create_function_with_type" { CREATE FUNCTION footype(num foo) RETURNS int AS 'select 1' LANGUAGE sql; } +step "s1_create_table_with_type" { CREATE TABLE tabtype(a footab); } +step "s1_commit" { COMMIT; } + +session "s2" + +step "s2_begin" { BEGIN; } +step "s2_drop_schema" { DROP SCHEMA testschema; } +step "s2_drop_foo_type" { DROP TYPE public.foo; } +step "s2_drop_footab_type" { DROP TYPE public.footab; } +step "s2_commit" { COMMIT; } + +permutation "s1_begin" "s1_create_function_in_schema" "s2_drop_schema" "s1_commit" +permutation "s2_begin" "s2_drop_schema" "s1_create_function_in_schema" "s2_commit" +permutation "s1_begin" "s1_create_function_with_type" "s2_drop_foo_type" "s1_commit" +permutation "s2_begin" "s2_drop_foo_type" "s1_create_function_with_type" "s2_commit" +permutation "s1_begin" "s1_create_table_with_type" "s2_drop_footab_type" "s1_commit" +permutation "s2_begin" "s2_drop_footab_type" "s1_create_table_with_type" "s2_commit" -- 2.34.1 --Nnmp7Q5BciyL9zub-- ^ permalink raw reply [nested|flat] 54+ messages in thread
end of thread, other threads:[~2024-03-29 15:43 UTC | newest] Thread overview: 54+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2018-06-29 07:41 [PATCH 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/3] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 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]> 2018-06-29 07:41 [PATCH 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH v23 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH v22 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/9] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/8] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/8] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2018-06-29 07:41 [PATCH 1/5] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v27 2/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v43 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v57 1/6] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v39 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v38 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 v48 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 v25 2/8] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v29 2/7] 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 v33 2/7] 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 v31 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 v41 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 v44 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v37 1/6] 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 v28 2/7] 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 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 v40 1/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2020-03-13 07:58 [PATCH v30 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 v35 2/7] sequential scan for dshash Kyotaro Horiguchi <[email protected]> 2024-03-29 15:43 [PATCH v2] Avoid orphaned objects dependencies Bertrand Drouvot <[email protected]>
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