Avoid looping over all type cache entries in TypeCacheRelCallback()

Currently when a single relcache entry gets invalidated,
TypeCacheRelCallback() has to loop over all type cache entries to find
appropriate typentry to invalidate.  Unfortunately, using the syscache here
is impossible, because this callback could be called outside a transaction
and this makes impossible catalog lookups.  This is why present commit
introduces RelIdToTypeIdCacheHash to map relation OID to its composite type
OID.

We are keeping RelIdToTypeIdCacheHash entry while corresponding type cache
entry have something to clean.  Therefore, RelIdToTypeIdCacheHash shouldn't
get bloat in the case of temporary tables flood.

Discussion: https://postgr.es/m/5812a6e5-68ae-4d84-9d85-b443176966a1%40sigaev.ru
Author: Teodor Sigaev
Reviewed-by: Aleksander Alekseev, Tom Lane, Michael Paquier, Roman Zharkov
Reviewed-by: Andrei Lepikhov, Pavel Borisov

Author: akorotkov

src/backend/utils/cache/typcache.c

@@ -77,6 +77,20 @@
 /* The main type cache hashtable searched by lookup_type_cache */
 static HTAB *TypeCacheHash = NULL;
 
+/*
+ * The mapping of relation's OID to the corresponding composite type OID.
+ * We're keeping the map entry when the corresponding typentry has something
+ * to clear i.e it has either TCFLAGS_HAVE_PG_TYPE_DATA, or
+ * TCFLAGS_OPERATOR_FLAGS, or tupdesc.
+ */
+static HTAB *RelIdToTypeIdCacheHash = NULL;
+
+typedef struct RelIdToTypeIdCacheEntry
+{
+	Oid			relid;			/* OID of the relation */
+	Oid			composite_typid;	/* OID of the relation's composite type */
+} RelIdToTypeIdCacheEntry;
+
 /* List of type cache entries for domain types */
 static TypeCacheEntry *firstDomainTypeEntry = NULL;
 
@@ -329,6 +343,8 @@ static void shared_record_typmod_registry_detach(dsm_segment *segment,
 static TupleDesc find_or_make_matching_shared_tupledesc(TupleDesc tupdesc);
 static dsa_pointer share_tupledesc(dsa_area *area, TupleDesc tupdesc,
 								   uint32 typmod);
+static void insert_rel_type_cache_if_needed(TypeCacheEntry *typentry);
+static void delete_rel_type_cache_if_needed(TypeCacheEntry *typentry);
 
 
 /*
@@ -376,6 +392,13 @@ lookup_type_cache(Oid type_id, int flags)
 		TypeCacheHash = hash_create("Type information cache", 64,
 									&ctl, HASH_ELEM | HASH_FUNCTION);
 
+		Assert(RelIdToTypeIdCacheHash == NULL);
+
+		ctl.keysize = sizeof(Oid);
+		ctl.entrysize = sizeof(RelIdToTypeIdCacheEntry);
+		RelIdToTypeIdCacheHash = hash_create("Map from relid to OID of cached composite type", 64,
+											 &ctl, HASH_ELEM | HASH_BLOBS);
+
 		/* Also set up callbacks for SI invalidations */
 		CacheRegisterRelcacheCallback(TypeCacheRelCallback, (Datum) 0);
 		CacheRegisterSyscacheCallback(TYPEOID, TypeCacheTypCallback, (Datum) 0);
@@ -387,6 +410,8 @@ lookup_type_cache(Oid type_id, int flags)
 			CreateCacheMemoryContext();
 	}
 
+	Assert(TypeCacheHash != NULL && RelIdToTypeIdCacheHash != NULL);
+
 	/* Try to look up an existing entry */
 	typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
 											  &type_id,
@@ -438,6 +463,7 @@ lookup_type_cache(Oid type_id, int flags)
 		typentry->typelem = typtup->typelem;
 		typentry->typcollation = typtup->typcollation;
 		typentry->flags |= TCFLAGS_HAVE_PG_TYPE_DATA;
+		insert_rel_type_cache_if_needed(typentry);
 
 		/* If it's a domain, immediately thread it into the domain cache list */
 		if (typentry->typtype == TYPTYPE_DOMAIN)
@@ -483,6 +509,7 @@ lookup_type_cache(Oid type_id, int flags)
 		typentry->typelem = typtup->typelem;
 		typentry->typcollation = typtup->typcollation;
 		typentry->flags |= TCFLAGS_HAVE_PG_TYPE_DATA;
+		insert_rel_type_cache_if_needed(typentry);
 
 		ReleaseSysCache(tp);
 	}
@@ -2281,6 +2308,53 @@ SharedRecordTypmodRegistryAttach(SharedRecordTypmodRegistry *registry)
 	CurrentSession->shared_typmod_table = typmod_table;
 }
 
+/*
+ * InvalidateCompositeTypeCacheEntry
+ *		Invalidate particular TypeCacheEntry on Relcache inval callback
+ *
+ * Delete the cached tuple descriptor (if any) for the given composite
+ * type, and reset whatever info we have cached about the composite type's
+ * comparability.
+ */
+static void
+InvalidateCompositeTypeCacheEntry(TypeCacheEntry *typentry)
+{
+	bool		hadTupDescOrOpclass;
+
+	Assert(typentry->typtype == TYPTYPE_COMPOSITE &&
+		   OidIsValid(typentry->typrelid));
+
+	hadTupDescOrOpclass = (typentry->tupDesc != NULL) ||
+		(typentry->flags & TCFLAGS_OPERATOR_FLAGS);
+
+	/* Delete tupdesc if we have it */
+	if (typentry->tupDesc != NULL)
+	{
+		/*
+		 * Release our refcount and free the tupdesc if none remain. We can't
+		 * use DecrTupleDescRefCount here because this reference is not logged
+		 * by the current resource owner.
+		 */
+		Assert(typentry->tupDesc->tdrefcount > 0);
+		if (--typentry->tupDesc->tdrefcount == 0)
+			FreeTupleDesc(typentry->tupDesc);
+		typentry->tupDesc = NULL;
+
+		/*
+		 * Also clear tupDesc_identifier, so that anyone watching it will
+		 * realize that the tupdesc has changed.
+		 */
+		typentry->tupDesc_identifier = 0;
+	}
+
+	/* Reset equality/comparison/hashing validity information */
+	typentry->flags &= ~TCFLAGS_OPERATOR_FLAGS;
+
+	/* Call check_delete_rel_type_cache() if we actually cleared something */
+	if (hadTupDescOrOpclass)
+		delete_rel_type_cache_if_needed(typentry);
+}
+
 /*
  * TypeCacheRelCallback
  *		Relcache inval callback function
@@ -2290,63 +2364,55 @@ SharedRecordTypmodRegistryAttach(SharedRecordTypmodRegistry *registry)
  * whatever info we have cached about the composite type's comparability.
  *
  * This is called when a relcache invalidation event occurs for the given
- * relid.  We must scan the whole typcache hash since we don't know the
- * type OID corresponding to the relid.  We could do a direct search if this
- * were a syscache-flush callback on pg_type, but then we would need all
- * ALTER-TABLE-like commands that could modify a rowtype to issue syscache
- * invals against the rel's pg_type OID.  The extra SI signaling could very
- * well cost more than we'd save, since in most usages there are not very
- * many entries in a backend's typcache.  The risk of bugs-of-omission seems
- * high, too.
- *
- * Another possibility, with only localized impact, is to maintain a second
- * hashtable that indexes composite-type typcache entries by their typrelid.
- * But it's still not clear it's worth the trouble.
+ * relid.  We can't use syscache to find a type corresponding to the given
+ * relation because the code can be called outside of transaction. Thus we use
+ * the RelIdToTypeIdCacheHash map to locate appropriate typcache entry.
  */
 static void
 TypeCacheRelCallback(Datum arg, Oid relid)
 {
-	HASH_SEQ_STATUS status;
 	TypeCacheEntry *typentry;
 
-	/* TypeCacheHash must exist, else this callback wouldn't be registered */
-	hash_seq_init(&status, TypeCacheHash);
-	while ((typentry = (TypeCacheEntry *) hash_seq_search(&status)) != NULL)
+	/*
+	 * RelIdToTypeIdCacheHash and TypeCacheHash should exist, otherwise this
+	 * callback wouldn't be registered
+	 */
+	if (OidIsValid(relid))
 	{
-		if (typentry->typtype == TYPTYPE_COMPOSITE)
+		RelIdToTypeIdCacheEntry *relentry;
+
+		/*
+		 * Find an RelIdToTypeIdCacheHash entry, which should exist as soon as
+		 * corresponding typcache entry has something to clean.
+		 */
+		relentry = (RelIdToTypeIdCacheEntry *) hash_search(RelIdToTypeIdCacheHash,
+														   &relid,
+														   HASH_FIND, NULL);
+
+		if (relentry != NULL)
 		{
-			/* Skip if no match, unless we're zapping all composite types */
-			if (relid != typentry->typrelid && relid != InvalidOid)
-				continue;
+			typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
+													  &relentry->composite_typid,
+													  HASH_FIND, NULL);
 
-			/* Delete tupdesc if we have it */
-			if (typentry->tupDesc != NULL)
+			if (typentry != NULL)
 			{
-				/*
-				 * Release our refcount, and free the tupdesc if none remain.
-				 * (Can't use DecrTupleDescRefCount because this reference is
-				 * not logged in current resource owner.)
-				 */
-				Assert(typentry->tupDesc->tdrefcount > 0);
-				if (--typentry->tupDesc->tdrefcount == 0)
-					FreeTupleDesc(typentry->tupDesc);
-				typentry->tupDesc = NULL;
+				Assert(typentry->typtype == TYPTYPE_COMPOSITE);
+				Assert(relid == typentry->typrelid);
 
-				/*
-				 * Also clear tupDesc_identifier, so that anything watching
-				 * that will realize that the tupdesc has possibly changed.
-				 * (Alternatively, we could specify that to detect possible
-				 * tupdesc change, one must check for tupDesc != NULL as well
-				 * as tupDesc_identifier being the same as what was previously
-				 * seen.  That seems error-prone.)
-				 */
-				typentry->tupDesc_identifier = 0;
+				InvalidateCompositeTypeCacheEntry(typentry);
 			}
-
-			/* Reset equality/comparison/hashing validity information */
-			typentry->flags &= ~TCFLAGS_OPERATOR_FLAGS;
 		}
-		else if (typentry->typtype == TYPTYPE_DOMAIN)
+
+		/*
+		 * Visit all the domain types sequentially.  Typically this shouldn't
+		 * affect performance since domain types are less tended to bloat.
+		 * Domain types are created manually, unlike composite types which are
+		 * automatically created for every temporary table.
+		 */
+		for (typentry = firstDomainTypeEntry;
+			 typentry != NULL;
+			 typentry = typentry->nextDomain)
 		{
 			/*
 			 * If it's domain over composite, reset flags.  (We don't bother
@@ -2358,6 +2424,36 @@ TypeCacheRelCallback(Datum arg, Oid relid)
 				typentry->flags &= ~TCFLAGS_OPERATOR_FLAGS;
 		}
 	}
+	else
+	{
+		HASH_SEQ_STATUS status;
+
+		/*
+		 * Relid is invalid. By convention we need to reset all composite
+		 * types in cache. Also, we should reset flags for domain types, and
+		 * we loop over all entries in hash, so, do it in a single scan.
+		 */
+		hash_seq_init(&status, TypeCacheHash);
+		while ((typentry = (TypeCacheEntry *) hash_seq_search(&status)) != NULL)
+		{
+			if (typentry->typtype == TYPTYPE_COMPOSITE)
+			{
+				InvalidateCompositeTypeCacheEntry(typentry);
+			}
+			else if (typentry->typtype == TYPTYPE_DOMAIN)
+			{
+				/*
+				 * If it's domain over composite, reset flags.  (We don't
+				 * bother trying to determine whether the specific base type
+				 * needs a reset.)  Note that if we haven't determined whether
+				 * the base type is composite, we don't need to reset
+				 * anything.
+				 */
+				if (typentry->flags & TCFLAGS_DOMAIN_BASE_IS_COMPOSITE)
+					typentry->flags &= ~TCFLAGS_OPERATOR_FLAGS;
+			}
+		}
+	}
 }
 
 /*
@@ -2388,6 +2484,8 @@ TypeCacheTypCallback(Datum arg, int cacheid, uint32 hashvalue)
 
 	while ((typentry = (TypeCacheEntry *) hash_seq_search(&status)) != NULL)
 	{
+		bool		hadPgTypeData = (typentry->flags & TCFLAGS_HAVE_PG_TYPE_DATA);
+
 		Assert(hashvalue == 0 || typentry->type_id_hash == hashvalue);
 
 		/*
@@ -2397,6 +2495,13 @@ TypeCacheTypCallback(Datum arg, int cacheid, uint32 hashvalue)
 		 */
 		typentry->flags &= ~(TCFLAGS_HAVE_PG_TYPE_DATA |
 							 TCFLAGS_CHECKED_DOMAIN_CONSTRAINTS);
+
+		/*
+		 * Call check_delete_rel_type_cache() if we cleaned
+		 * TCFLAGS_HAVE_PG_TYPE_DATA flag previously.
+		 */
+		if (hadPgTypeData)
+			delete_rel_type_cache_if_needed(typentry);
 	}
 }
 
@@ -2905,3 +3010,85 @@ shared_record_typmod_registry_detach(dsm_segment *segment, Datum datum)
 	}
 	CurrentSession->shared_typmod_registry = NULL;
 }
+
+/*
+ * Insert RelIdToTypeIdCacheHash entry after setting of the
+ * TCFLAGS_HAVE_PG_TYPE_DATA flag if needed.
+ */
+static void
+insert_rel_type_cache_if_needed(TypeCacheEntry *typentry)
+{
+	Assert(typentry->flags & TCFLAGS_HAVE_PG_TYPE_DATA);
+
+	/* Immediately quit for non-composite types */
+	if (typentry->typtype != TYPTYPE_COMPOSITE)
+		return;
+
+	/* typrelid should be given for composite types */
+	Assert(OidIsValid(typentry->typrelid));
+
+	/*
+	 * Insert a RelIdToTypeIdCacheHash entry if the typentry doesn't have any
+	 * information indicating there should be such an entry already.
+	 */
+	if (!(typentry->flags & TCFLAGS_OPERATOR_FLAGS) &&
+		typentry->tupDesc == NULL)
+	{
+		RelIdToTypeIdCacheEntry *relentry;
+		bool		found;
+
+		relentry = (RelIdToTypeIdCacheEntry *) hash_search(RelIdToTypeIdCacheHash,
+														   &typentry->typrelid,
+														   HASH_ENTER, &found);
+		Assert(!found);
+		relentry->relid = typentry->typrelid;
+		relentry->composite_typid = typentry->type_id;
+	}
+}
+
+/*
+ * Delete entry RelIdToTypeIdCacheHash if needed after resetting of the
+ * TCFLAGS_HAVE_PG_TYPE_DATA flag, or any of TCFLAGS_OPERATOR_FLAGS flags,
+ * or tupDesc.
+ */
+static void
+delete_rel_type_cache_if_needed(TypeCacheEntry *typentry)
+{
+	/* Immediately quit for non-composite types */
+	if (typentry->typtype != TYPTYPE_COMPOSITE)
+		return;
+
+	/* typrelid should be given for composite types */
+	Assert(OidIsValid(typentry->typrelid));
+
+	/*
+	 * Delete a RelIdToTypeIdCacheHash entry if the typentry doesn't have any
+	 * information indicating entry should be still there.
+	 */
+	if (!(typentry->flags & TCFLAGS_HAVE_PG_TYPE_DATA) &&
+		!(typentry->flags & TCFLAGS_OPERATOR_FLAGS) &&
+		typentry->tupDesc == NULL)
+	{
+		bool		found;
+
+		(void) hash_search(RelIdToTypeIdCacheHash,
+						   &typentry->typrelid,
+						   HASH_REMOVE, &found);
+		Assert(found);
+	}
+	else
+	{
+#ifdef USE_ASSERT_CHECKING
+		/*
+		 * In assert-enabled builds otherwise check for RelIdToTypeIdCacheHash
+		 * entry if it should exist.
+		 */
+		bool		found;
+
+		(void) hash_search(RelIdToTypeIdCacheHash,
+						   &typentry->typrelid,
+						   HASH_FIND, &found);
+		Assert(found);
+#endif
+	}
+}

src/tools/pgindent/typedefs.list

@@ -2377,6 +2377,7 @@ RelFileLocator
 RelFileLocatorBackend
 RelFileNumber
 RelIdCacheEnt
+RelIdToTypeIdCacheEntry
 RelInfo
 RelInfoArr
 RelMapFile