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[PATCH v24 2/5] Add conditional lock feature to dshash
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* [PATCH 2/5] Add conditional lock feature to dshash
@ 2018-09-27 02:15 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2018-09-27 02:15 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. This commit adds new
interfaces for dshash_find and dshash_find_or_insert. The new
interfaces have an extra parameter "nowait" taht commands not to wait
for lock.
---
 src/backend/lib/dshash.c | 64 +++++++++++++++++++++++++++++++++++++---
 src/include/lib/dshash.h |  6 ++++
 2 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 7675370058..7766fa7704 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -394,19 +394,51 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  */
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
+{
+	return dshash_find_extended(hash_table, key, exclusive, false, NULL);
+}
+
+/*
+ * The version of dshash_find, which is allowed to return immediately on lock
+ * failure. Lock status is set to *lock_failed in that case.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool *lock_acquired)
 {
 	dshash_hash hash;
 	size_t		partition;
 	dshash_table_item *item;
 
+	/*
+	 * No need to return lock resut when !nowait. Otherwise the caller may
+	 * omit the lock result when NULL is returned.
+	 */
+	Assert(nowait || !lock_acquired);
+
 	hash = hash_key(hash_table, key);
 	partition = PARTITION_FOR_HASH(hash);
 
 	Assert(hash_table->control->magic == DSHASH_MAGIC);
 	Assert(!hash_table->find_locked);
 
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
+	if (nowait)
+	{
+		if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partition),
+									  exclusive ? LW_EXCLUSIVE : LW_SHARED))
+		{
+			if (lock_acquired)
+				*lock_acquired = false;
+			return NULL;
+		}
+	}
+	else
+		LWLockAcquire(PARTITION_LOCK(hash_table, partition),
+					  exclusive ? LW_EXCLUSIVE : LW_SHARED);
+
+	if (lock_acquired)
+		*lock_acquired = true;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
@@ -441,6 +473,22 @@ void *
 dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
+{
+	return dshash_find_or_insert_extended(hash_table, key, found, false);
+}
+
+/*
+ * The version of dshash_find_or_insert, which is allowed to return immediately
+ * on lock failure.
+ *
+ * Notes above dshash_find_extended() regarding locking and error handling
+ * equally apply here.
+ */
+void *
+dshash_find_or_insert_extended(dshash_table *hash_table,
+							   const void *key,
+							   bool *found,
+							   bool nowait)
 {
 	dshash_hash hash;
 	size_t		partition_index;
@@ -455,8 +503,16 @@ dshash_find_or_insert(dshash_table *hash_table,
 	Assert(!hash_table->find_locked);
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (nowait)
+	{
+		if (!LWLockConditionalAcquire(
+				PARTITION_LOCK(hash_table, partition_index),
+				LW_EXCLUSIVE))
+			return NULL;
+	}
+	else
+		LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
+					  LW_EXCLUSIVE);
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index ad88f32cdd..a7d19c6a85 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -89,8 +89,14 @@ 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);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait,
+								  bool *lock_acquired);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_or_insert_extended(dshash_table *hash_table,
+											const void *key, bool *found,
+											bool nowait);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v24 2/5] Add conditional lock feature to dshash
@ 2018-09-27 02:15 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2018-09-27 02:15 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. This commit adds new
interfaces for dshash_find and dshash_find_or_insert. The new
interfaces have an extra parameter "nowait" taht commands not to wait
for lock.
---
 src/backend/lib/dshash.c | 69 ++++++++++++++++++++++++++++++++++++----
 src/include/lib/dshash.h |  6 ++++
 2 files changed, 68 insertions(+), 7 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 4f0c7ec840..60a6e3c0bc 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -394,19 +394,48 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  */
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
+{
+	return dshash_find_extended(hash_table, key, exclusive, false, NULL);
+}
+
+/*
+ * Addition to dshash_find, returns immediately when nowait is true and lock
+ * was not acquired. Lock status is set to *lock_failed if any.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool *lock_acquired)
 {
 	dshash_hash hash;
 	size_t		partition;
 	dshash_table_item *item;
 
+	/* allowing !nowait returning the result is just not sensible */
+	Assert(nowait || !lock_acquired);
+
 	hash = hash_key(hash_table, key);
 	partition = PARTITION_FOR_HASH(hash);
 
 	Assert(hash_table->control->magic == DSHASH_MAGIC);
 	Assert(!hash_table->find_locked);
 
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
+	if (nowait)
+	{
+		if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partition),
+									  exclusive ? LW_EXCLUSIVE : LW_SHARED))
+		{
+			if (lock_acquired)
+				*lock_acquired = false;
+			return NULL;
+		}
+	}
+	else
+		LWLockAcquire(PARTITION_LOCK(hash_table, partition),
+					  exclusive ? LW_EXCLUSIVE : LW_SHARED);
+
+	if (lock_acquired)
+		*lock_acquired = true;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
@@ -441,6 +470,22 @@ void *
 dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
+{
+	return dshash_find_or_insert_extended(hash_table, key, found, false);
+}
+
+/*
+ * Addition to dshash_find_or_insert, returns NULL if nowait is true and lock
+ * was not acquired.
+ *
+ * Notes above dshash_find_extended() regarding locking and error handling
+ * equally apply here.
+ */
+void *
+dshash_find_or_insert_extended(dshash_table *hash_table,
+							   const void *key,
+							   bool *found,
+							   bool nowait)
 {
 	dshash_hash hash;
 	size_t		partition_index;
@@ -455,8 +500,16 @@ dshash_find_or_insert(dshash_table *hash_table,
 	Assert(!hash_table->find_locked);
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (nowait)
+	{
+		if (!LWLockConditionalAcquire(
+				PARTITION_LOCK(hash_table, partition_index),
+				LW_EXCLUSIVE))
+			return NULL;
+	}
+	else
+		LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
+					  LW_EXCLUSIVE);
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
@@ -626,9 +679,11 @@ dshash_memhash(const void *v, size_t size, void *arg)
  * 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).
+ * 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), and the locks are held until the end of the scan.
+ * Otherwise the partition locks are acquired and released as needed
+ * during the scan (up to two partitions may be locked at the same time).
  */
 void
 dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table,
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index 79698a6ad6..67f7d77f71 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -90,8 +90,14 @@ 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);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait,
+								  bool *lock_acquired);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_or_insert_extended(dshash_table *hash_table,
+											const void *key, bool *found,
+											bool nowait);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v24-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v45 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v45-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v48 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v48-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v48 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v48-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v49 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v49-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v47 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v47-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v46 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v46-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v45 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v45-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v46 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v46-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v47 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v47-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v45 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v45-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v52 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v52-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v46 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v46-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v52 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v52-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v45 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v45-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v48 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v48-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v49 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v49-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v48 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v48-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v46 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v46-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v45 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v45-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v48 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v48-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v48 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v48-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v52 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v52-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v47 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v47-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v46 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v46-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v48 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v48-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v45 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v45-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v52 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v52-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v47 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v47-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v49 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v49-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v49 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v49-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v46 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v46-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v40 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index b829167872..9c90096f3d 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index c337099061..493e974832 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v40-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v49 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v49-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v49 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v49-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v50 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v50-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v45 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v45-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v47 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v47-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v51 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v51-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v56 2/6] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 29ad767618..f79b6de245 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v56-0003-Shared-memory-based-stats-collector.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v47 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v47-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v34 3/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 1ef093e2e9..d7ee6de11e 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index 0ca9514021..5f7a60febd 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v34-0004-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v48 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
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="v48-0003-Make-archiver-process-an-auxiliary-process.patch"



^ permalink  raw  reply  [nested|flat] 235+ messages in thread

* [PATCH v45 2/7] Add conditional lock feature to dshash
@ 2020-03-13 07:58 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 235+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-13 07:58 UTC (permalink / raw)

Dshash currently waits for lock unconditionally. It is inconvenient
when we want to avoid being blocked by other processes. This commit
adds alternative functions of dshash_find and dshash_find_or_insert
that allows immediate return on lock failure.
---
 src/backend/lib/dshash.c | 98 +++++++++++++++++++++-------------------
 src/include/lib/dshash.h |  3 ++
 2 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
index 520bfa0979..853d78b528 100644
--- a/src/backend/lib/dshash.c
+++ b/src/backend/lib/dshash.c
@@ -383,6 +383,10 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
  * the caller must take care to ensure that the entry is not left corrupted.
  * The lock mode is either shared or exclusive depending on 'exclusive'.
  *
+ * If found is not NULL, *found is set to true if the key is found in the hash
+ * table. If the key is not found, *found is set to false and a pointer to a
+ * newly created entry is returned.
+ *
  * The caller must not lock a lock already.
  *
  * Note that the lock held is in fact an LWLock, so interrupts will be held on
@@ -392,36 +396,7 @@ dshash_get_hash_table_handle(dshash_table *hash_table)
 void *
 dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
 {
-	dshash_hash hash;
-	size_t		partition;
-	dshash_table_item *item;
-
-	hash = hash_key(hash_table, key);
-	partition = PARTITION_FOR_HASH(hash);
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
-
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition),
-				  exclusive ? LW_EXCLUSIVE : LW_SHARED);
-	ensure_valid_bucket_pointers(hash_table);
-
-	/* Search the active bucket. */
-	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
-
-	if (!item)
-	{
-		/* Not found. */
-		LWLockRelease(PARTITION_LOCK(hash_table, partition));
-		return NULL;
-	}
-	else
-	{
-		/* The caller will free the lock by calling dshash_release_lock. */
-		hash_table->find_locked = true;
-		hash_table->find_exclusively_locked = exclusive;
-		return ENTRY_FROM_ITEM(item);
-	}
+	return dshash_find_extended(hash_table, key, exclusive, false, false, NULL);
 }
 
 /*
@@ -439,31 +414,60 @@ dshash_find_or_insert(dshash_table *hash_table,
 					  const void *key,
 					  bool *found)
 {
-	dshash_hash hash;
-	size_t		partition_index;
-	dshash_partition *partition;
+	return dshash_find_extended(hash_table, key, true, false, true, found);
+}
+
+
+/*
+ * Find the key in the hash table.
+ *
+ * "exclusive" is the lock mode in which the partition for the returned item
+ * is locked.  If "nowait" is true, the function immediately returns if
+ * required lock was not acquired.  "insert" indicates insert mode. In this
+ * mode new entry is inserted and set *found to false. *found is set to true if
+ * found. "found" must be non-null in this mode.
+ */
+void *
+dshash_find_extended(dshash_table *hash_table, const void *key,
+					 bool exclusive, bool nowait, bool insert, bool *found)
+{
+	dshash_hash hash = hash_key(hash_table, key);
+	size_t		partidx = PARTITION_FOR_HASH(hash);
+	dshash_partition *partition = &hash_table->control->partitions[partidx];
+	LWLockMode  lockmode = exclusive ? LW_EXCLUSIVE : LW_SHARED;
 	dshash_table_item *item;
 
-	hash = hash_key(hash_table, key);
-	partition_index = PARTITION_FOR_HASH(hash);
-	partition = &hash_table->control->partitions[partition_index];
-
-	Assert(hash_table->control->magic == DSHASH_MAGIC);
-	Assert(!hash_table->find_locked);
+	/* must be exclusive when insert allowed */
+	Assert(!insert || (exclusive && found != NULL));
 
 restart:
-	LWLockAcquire(PARTITION_LOCK(hash_table, partition_index),
-				  LW_EXCLUSIVE);
+	if (!nowait)
+		LWLockAcquire(PARTITION_LOCK(hash_table, partidx), lockmode);
+	else if (!LWLockConditionalAcquire(PARTITION_LOCK(hash_table, partidx),
+									   lockmode))
+		return NULL;
+
 	ensure_valid_bucket_pointers(hash_table);
 
 	/* Search the active bucket. */
 	item = find_in_bucket(hash_table, key, BUCKET_FOR_HASH(hash_table, hash));
 
 	if (item)
-		*found = true;
+	{
+		if (found)
+			*found = true;
+	}
 	else
 	{
-		*found = false;
+		if (found)
+			*found = false;
+
+		if (!insert)
+		{
+			/* The caller didn't told to add a new entry. */
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+			return NULL;
+		}
 
 		/* Check if we are getting too full. */
 		if (partition->count > MAX_COUNT_PER_PARTITION(hash_table))
@@ -479,7 +483,8 @@ restart:
 			 * Give up our existing lock first, because resizing needs to
 			 * reacquire all the locks in the right order to avoid deadlocks.
 			 */
-			LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
+			LWLockRelease(PARTITION_LOCK(hash_table, partidx));
+
 			resize(hash_table, hash_table->size_log2 + 1);
 
 			goto restart;
@@ -493,12 +498,13 @@ restart:
 		++partition->count;
 	}
 
-	/* The caller must release the lock with dshash_release_lock. */
+	/* The caller will free the lock by calling dshash_release_lock. */
 	hash_table->find_locked = true;
-	hash_table->find_exclusively_locked = true;
+	hash_table->find_exclusively_locked = exclusive;
 	return ENTRY_FROM_ITEM(item);
 }
 
+
 /*
  * Remove an entry by key.  Returns true if the key was found and the
  * corresponding entry was removed.
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h
index a6ea377173..5b8114d041 100644
--- a/src/include/lib/dshash.h
+++ b/src/include/lib/dshash.h
@@ -91,6 +91,9 @@ extern void *dshash_find(dshash_table *hash_table,
 						 const void *key, bool exclusive);
 extern void *dshash_find_or_insert(dshash_table *hash_table,
 								   const void *key, bool *found);
+extern void *dshash_find_extended(dshash_table *hash_table, const void *key,
+								  bool exclusive, bool nowait, bool insert,
+								  bool *found);
 extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
 extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
 extern void dshash_release_lock(dshash_table *hash_table, void *entry);
-- 
2.27.0


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 filename="v45-0003-Make-archiver-process-an-auxiliary-process.patch"



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