Merge pull request #456 from citusdata/367-drop-extension-messages

DROP EXTENSION without any warnings

src/backend/distributed/executor/multi_utility.c

@@ -66,7 +66,6 @@ static void ErrorIfUnsupportedAlterTableStmt(AlterTableStmt *alterTableStatement
 static void ErrorIfDistributedRenameStmt(RenameStmt *renameStatement);
 
 /* Local functions forward declarations for helper functions */
-static void WarnIfDropCitusExtension(DropStmt *dropStatement);
 static bool IsAlterTableRenameStmt(RenameStmt *renameStatement);
 static void ExecuteDistributedDDLCommand(Oid relationId, const char *ddlCommandString);
 static bool ExecuteCommandOnWorkerShards(Oid relationId, const char *commandString,
@@ -143,10 +142,6 @@ multi_ProcessUtility(Node *parsetree,
 		{
 			parsetree = ProcessDropIndexStmt(dropStatement, queryString);
 		}
-		else if (dropStatement->removeType == OBJECT_EXTENSION)
-		{
-			WarnIfDropCitusExtension(dropStatement);
-		}
 	}
 
 	if (IsA(parsetree, AlterTableStmt))
@@ -208,37 +203,6 @@ multi_ProcessUtility(Node *parsetree,
 }
 
 
-/*
- * WarnIfDropCitusExtension prints a WARNING if dropStatement includes dropping
- * citus extension.
- */
-static void
-WarnIfDropCitusExtension(DropStmt *dropStatement)
-{
-	ListCell *dropStatementObject = NULL;
-
-	Assert(dropStatement->removeType == OBJECT_EXTENSION);
-
-	foreach(dropStatementObject, dropStatement->objects)
-	{
-		List *objectNameList = lfirst(dropStatementObject);
-		char *objectName = NameListToString(objectNameList);
-
-		/* we're only concerned with the citus extension */
-		if (strncmp("citus", objectName, NAMEDATALEN) == 0)
-		{
-			/*
-			 * Warn the user about the possibility of invalid cache. Also, see
-			 * function comment of CachedRelationLookup().
-			 */
-			ereport(WARNING, (errmsg("could not clean the metadata cache on "
-									 "DROP EXTENSION command"),
-							  errhint("Reconnect to the server again.")));
-		}
-	}
-}
-
-
 /* Is the passed in statement a transmit statement? */
 static bool
 IsTransmitStmt(Node *parsetree)

src/backend/distributed/utils/metadata_cache.c

@@ -12,6 +12,7 @@
 #include "access/genam.h"
 #include "access/heapam.h"
 #include "access/htup_details.h"
+#include "access/xact.h"
 #include "catalog/indexing.h"
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_type.h"
@@ -35,6 +36,17 @@
 #include "utils/syscache.h"
 
 
+/* state which should be cleared upon DROP EXTENSION */
+static bool extensionLoaded = false;
+static Oid distShardRelationId = InvalidOid;
+static Oid distShardPlacementRelationId = InvalidOid;
+static Oid distPartitionRelationId = InvalidOid;
+static Oid distPartitionLogicalRelidIndexId = InvalidOid;
+static Oid distShardLogicalRelidIndexId = InvalidOid;
+static Oid distShardShardidIndexId = InvalidOid;
+static Oid distShardPlacementShardidIndexId = InvalidOid;
+static Oid extraDataContainerFuncId = InvalidOid;
+
 /* Hash table for informations about each partition */
 static HTAB *DistTableCacheHash = NULL;
 
@@ -297,16 +309,10 @@ LookupDistTableCacheEntry(Oid relationId)
  * CitusHasBeenLoaded returns true if the citus extension has been created
  * in the current database and the extension script has been executed. Otherwise,
  * it returns false. The result is cached as this is called very frequently.
- *
- * NB: The way this is cached means the result will be wrong after the
- * extension is dropped. A reconnect fixes that though, so that seems
- * acceptable.
  */
 bool
 CitusHasBeenLoaded(void)
 {
-	static bool extensionLoaded = false;
-
 	/* recheck presence until citus has been loaded */
 	if (!extensionLoaded)
 	{
@@ -329,6 +335,19 @@ CitusHasBeenLoaded(void)
 		}
 
 		extensionLoaded = extensionPresent && extensionScriptExecuted;
+
+		if (extensionLoaded)
+		{
+			/*
+			 * InvalidateDistRelationCacheCallback resets state such as extensionLoaded
+			 * when it notices changes to pg_dist_partition (which usually indicate
+			 * `DROP EXTENSION citus;` has been run)
+			 *
+			 * Ensure InvalidateDistRelationCacheCallback will notice those changes
+			 * by caching pg_dist_partition's oid.
+			 */
+			DistPartitionRelationId();
+		}
 	}
 
 	return extensionLoaded;
@@ -339,11 +358,9 @@ CitusHasBeenLoaded(void)
 Oid
 DistShardRelationId(void)
 {
-	static Oid cachedOid = InvalidOid;
+	CachedRelationLookup("pg_dist_shard", &distShardRelationId);
 
-	CachedRelationLookup("pg_dist_shard", &cachedOid);
-
-	return cachedOid;
+	return distShardRelationId;
 }
 
 
@@ -351,11 +368,9 @@ DistShardRelationId(void)
 Oid
 DistShardPlacementRelationId(void)
 {
-	static Oid cachedOid = InvalidOid;
+	CachedRelationLookup("pg_dist_shard_placement", &distShardPlacementRelationId);
 
-	CachedRelationLookup("pg_dist_shard_placement", &cachedOid);
-
-	return cachedOid;
+	return distShardPlacementRelationId;
 }
 
 
@@ -363,11 +378,9 @@ DistShardPlacementRelationId(void)
 Oid
 DistPartitionRelationId(void)
 {
-	static Oid cachedOid = InvalidOid;
+	CachedRelationLookup("pg_dist_partition", &distPartitionRelationId);
 
-	CachedRelationLookup("pg_dist_partition", &cachedOid);
-
-	return cachedOid;
+	return distPartitionRelationId;
 }
 
 
@@ -375,11 +388,10 @@ DistPartitionRelationId(void)
 Oid
 DistPartitionLogicalRelidIndexId(void)
 {
-	static Oid cachedOid = InvalidOid;
+	CachedRelationLookup("pg_dist_partition_logical_relid_index",
+						 &distPartitionLogicalRelidIndexId);
 
-	CachedRelationLookup("pg_dist_partition_logical_relid_index", &cachedOid);
-
-	return cachedOid;
+	return distPartitionLogicalRelidIndexId;
 }
 
 
@@ -387,11 +399,10 @@ DistPartitionLogicalRelidIndexId(void)
 Oid
 DistShardLogicalRelidIndexId(void)
 {
-	static Oid cachedOid = InvalidOid;
+	CachedRelationLookup("pg_dist_shard_logical_relid_index",
+						 &distShardLogicalRelidIndexId);
 
-	CachedRelationLookup("pg_dist_shard_logical_relid_index", &cachedOid);
-
-	return cachedOid;
+	return distShardLogicalRelidIndexId;
 }
 
 
@@ -399,11 +410,9 @@ DistShardLogicalRelidIndexId(void)
 Oid
 DistShardShardidIndexId(void)
 {
-	static Oid cachedOid = InvalidOid;
+	CachedRelationLookup("pg_dist_shard_shardid_index", &distShardShardidIndexId);
 
-	CachedRelationLookup("pg_dist_shard_shardid_index", &cachedOid);
-
-	return cachedOid;
+	return distShardShardidIndexId;
 }
 
 
@@ -411,11 +420,10 @@ DistShardShardidIndexId(void)
 Oid
 DistShardPlacementShardidIndexId(void)
 {
-	static Oid cachedOid = InvalidOid;
+	CachedRelationLookup("pg_dist_shard_placement_shardid_index",
+						 &distShardPlacementShardidIndexId);
 
-	CachedRelationLookup("pg_dist_shard_placement_shardid_index", &cachedOid);
-
-	return cachedOid;
+	return distShardPlacementShardidIndexId;
 }
 
 
@@ -423,18 +431,17 @@ DistShardPlacementShardidIndexId(void)
 Oid
 CitusExtraDataContainerFuncId(void)
 {
-	static Oid cachedOid = 0;
 	List *nameList = NIL;
 	Oid paramOids[1] = { INTERNALOID };
 
-	if (cachedOid == InvalidOid)
+	if (extraDataContainerFuncId == InvalidOid)
 	{
 		nameList = list_make2(makeString("pg_catalog"),
 							  makeString("citus_extradata_container"));
-		cachedOid = LookupFuncName(nameList, 1, paramOids, false);
+		extraDataContainerFuncId = LookupFuncName(nameList, 1, paramOids, false);
 	}
 
-	return cachedOid;
+	return extraDataContainerFuncId;
 }
 
 
@@ -677,6 +684,24 @@ InvalidateDistRelationCacheCallback(Datum argument, Oid relationId)
 			cacheEntry->isValid = false;
 		}
 	}
+
+	/*
+	 * If pg_dist_partition is being invalidated drop all state
+	 * This happens pretty rarely, but most importantly happens during
+	 * DROP EXTENSION citus;
+	 */
+	if (relationId != InvalidOid && relationId == distPartitionRelationId)
+	{
+		extensionLoaded = false;
+		distShardRelationId = InvalidOid;
+		distShardPlacementRelationId = InvalidOid;
+		distPartitionRelationId = InvalidOid;
+		distPartitionLogicalRelidIndexId = InvalidOid;
+		distShardLogicalRelidIndexId = InvalidOid;
+		distShardShardidIndexId = InvalidOid;
+		distShardPlacementShardidIndexId = InvalidOid;
+		extraDataContainerFuncId = InvalidOid;
+	}
 }
 
 
@@ -878,10 +903,6 @@ TupleToShardInterval(HeapTuple heapTuple, TupleDesc tupleDescriptor, Oid interva
 /*
  * CachedRelationLookup performs a cached lookup for the relation
  * relationName, with the result cached in *cachedOid.
- *
- * NB: The way this is cached means the result will be wrong after the
- * extension is dropped and reconnect. A reconnect fixes that though, so that
- * seems acceptable.
  */
 static void
 CachedRelationLookup(const char *relationName, Oid *cachedOid)

src/test/regress/expected/multi_drop_extension.out

@@ -0,0 +1,39 @@
+--
+-- MULTI_DROP_EXTENSION
+--
+-- Tests around dropping and recreating the extension
+CREATE TABLE testtableddl(somecol int, distributecol text NOT NULL);
+SELECT master_create_distributed_table('testtableddl', 'distributecol', 'append');
+ master_create_distributed_table 
+---------------------------------
+ 
+(1 row)
+
+-- this emits a NOTICE message for every table we are dropping with our CASCADE. It would
+-- be nice to check that we get those NOTICE messages, but it's nicer to not have to
+-- change this test every time the previous tests change the set of tables they leave
+-- around.
+SET client_min_messages TO 'WARNING';
+DROP EXTENSION citus CASCADE;
+RESET client_min_messages;
+CREATE EXTENSION citus;
+-- verify that a table can be created after the extension has been dropped and recreated
+CREATE TABLE testtableddl(somecol int, distributecol text NOT NULL);
+SELECT master_create_distributed_table('testtableddl', 'distributecol', 'append');
+ master_create_distributed_table 
+---------------------------------
+ 
+(1 row)
+
+SELECT 1 FROM master_create_empty_shard('testtableddl');
+ ?column? 
+----------
+        1
+(1 row)
+
+SELECT * FROM testtableddl;
+ somecol | distributecol 
+---------+---------------
+(0 rows)
+
+DROP TABLE testtableddl;

src/test/regress/expected/multi_table_ddl.out

@@ -11,8 +11,6 @@ SELECT master_create_distributed_table('testtableddl', 'distributecol', 'append'
 
 -- verify that the citus extension can't be dropped while distributed tables exist
 DROP EXTENSION citus;
-WARNING:  could not clean the metadata cache on DROP EXTENSION command
-HINT:  Reconnect to the server again.
 ERROR:  cannot drop extension citus because other objects depend on it
 DETAIL:  table testtableddl depends on extension citus
 HINT:  Use DROP ... CASCADE to drop the dependent objects too.
@@ -62,11 +60,6 @@ SELECT * FROM pg_dist_shard_placement;
 ---------+------------+-------------+----------+----------
 (0 rows)
 
--- check that the extension now can be dropped (and recreated). We reconnect
--- before creating the extension to expire extension specific variables which
--- are cached for performance.
+-- check that the extension now can be dropped (and recreated)
 DROP EXTENSION citus;
-WARNING:  could not clean the metadata cache on DROP EXTENSION command
-HINT:  Reconnect to the server again.
-\c
 CREATE EXTENSION citus;

src/test/regress/multi_schedule

@@ -135,3 +135,8 @@ test: multi_router_planner
 # multi_large_shardid stages more shards into lineitem
 # ----------
 test: multi_large_shardid
+
+# ----------
+# multi_drop_extension makes sure we can safely drop and recreate the extension
+# ----------
+test: multi_drop_extension

src/test/regress/sql/multi_drop_extension.sql

@@ -0,0 +1,25 @@
+--
+-- MULTI_DROP_EXTENSION
+--
+-- Tests around dropping and recreating the extension
+
+
+CREATE TABLE testtableddl(somecol int, distributecol text NOT NULL);
+SELECT master_create_distributed_table('testtableddl', 'distributecol', 'append');
+
+-- this emits a NOTICE message for every table we are dropping with our CASCADE. It would
+-- be nice to check that we get those NOTICE messages, but it's nicer to not have to
+-- change this test every time the previous tests change the set of tables they leave
+-- around.
+SET client_min_messages TO 'WARNING';
+DROP EXTENSION citus CASCADE;
+RESET client_min_messages;
+
+CREATE EXTENSION citus;
+
+-- verify that a table can be created after the extension has been dropped and recreated
+CREATE TABLE testtableddl(somecol int, distributecol text NOT NULL);
+SELECT master_create_distributed_table('testtableddl', 'distributecol', 'append');
+SELECT 1 FROM master_create_empty_shard('testtableddl');
+SELECT * FROM testtableddl;
+DROP TABLE testtableddl;

src/test/regress/sql/multi_table_ddl.sql

@@ -34,9 +34,6 @@ SELECT * FROM pg_dist_partition;
 SELECT * FROM pg_dist_shard;
 SELECT * FROM pg_dist_shard_placement;
 
--- check that the extension now can be dropped (and recreated). We reconnect
--- before creating the extension to expire extension specific variables which
--- are cached for performance.
+-- check that the extension now can be dropped (and recreated)
 DROP EXTENSION citus;
-\c
 CREATE EXTENSION citus;