6 files changed, 76 insertions, 14 deletions

diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index 4c1d909d380..a68d945f2e7 100644
--- a/src/backend/commands/createas.c
+++ b/src/backend/commands/createas.c
@@ -243,15 +243,27 @@ ExecCreateTableAs(CreateTableAsStmt *stmt, const char *queryString,
 	if (stmt->if_not_exists)
 	{
 		Oid			nspid;
+		Oid			oldrelid;
 
-		nspid = RangeVarGetCreationNamespace(stmt->into->rel);
+		nspid = RangeVarGetCreationNamespace(into->rel);
 
-		if (get_relname_relid(stmt->into->rel->relname, nspid))
+		oldrelid = get_relname_relid(into->rel->relname, nspid);
+		if (OidIsValid(oldrelid))
 		{
+			/*
+			 * The relation exists and IF NOT EXISTS has been specified.
+			 *
+			 * If we are in an extension script, insist that the pre-existing
+			 * object be a member of the extension, to avoid security risks.
+			 */
+			ObjectAddressSet(address, RelationRelationId, oldrelid);
+			checkMembershipInCurrentExtension(&address);
+
+			/* OK to skip */
 			ereport(NOTICE,
 					(errcode(ERRCODE_DUPLICATE_TABLE),
 					 errmsg("relation \"%s\" already exists, skipping",
-							stmt->into->rel->relname)));
+							into->rel->relname)));
 			return InvalidObjectAddress;
 		}
 	}
diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index d7bc6e35f02..bc583c689c2 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -887,13 +887,22 @@ CreateForeignServer(CreateForeignServerStmt *stmt)
 	ownerId = GetUserId();
 
 	/*
-	 * Check that there is no other foreign server by this name. Do nothing if
-	 * IF NOT EXISTS was enforced.
+	 * Check that there is no other foreign server by this name.  If there is
+	 * one, do nothing if IF NOT EXISTS was specified.
 	 */
-	if (GetForeignServerByName(stmt->servername, true) != NULL)
+	srvId = get_foreign_server_oid(stmt->servername, true);
+	if (OidIsValid(srvId))
 	{
 		if (stmt->if_not_exists)
 		{
+			/*
+			 * If we are in an extension script, insist that the pre-existing
+			 * object be a member of the extension, to avoid security risks.
+			 */
+			ObjectAddressSet(myself, ForeignServerRelationId, srvId);
+			checkMembershipInCurrentExtension(&myself);
+
+			/* OK to skip */
 			ereport(NOTICE,
 					(errcode(ERRCODE_DUPLICATE_OBJECT),
 					 errmsg("server \"%s\" already exists, skipping",
@@ -1182,6 +1191,10 @@ CreateUserMapping(CreateUserMappingStmt *stmt)
 	{
 		if (stmt->if_not_exists)
 		{
+			/*
+			 * Since user mappings aren't members of extensions (see comments
+			 * below), no need for checkMembershipInCurrentExtension here.
+			 */
 			ereport(NOTICE,
 					(errcode(ERRCODE_DUPLICATE_OBJECT),
 					 errmsg("user mapping for \"%s\" already exists for server \"%s\", skipping",
diff --git a/src/backend/commands/schemacmds.c b/src/backend/commands/schemacmds.c
index 6cf94a3140b..6bc4edc321f 100644
--- a/src/backend/commands/schemacmds.c
+++ b/src/backend/commands/schemacmds.c
@@ -113,14 +113,25 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString,
 	 * the permissions checks, but since CREATE TABLE IF NOT EXISTS makes its
 	 * creation-permission check first, we do likewise.
 	 */
-	if (stmt->if_not_exists &&
-		SearchSysCacheExists1(NAMESPACENAME, PointerGetDatum(schemaName)))
+	if (stmt->if_not_exists)
 	{
-		ereport(NOTICE,
-				(errcode(ERRCODE_DUPLICATE_SCHEMA),
-				 errmsg("schema \"%s\" already exists, skipping",
-						schemaName)));
-		return InvalidOid;
+		namespaceId = get_namespace_oid(schemaName, true);
+		if (OidIsValid(namespaceId))
+		{
+			/*
+			 * If we are in an extension script, insist that the pre-existing
+			 * object be a member of the extension, to avoid security risks.
+			 */
+			ObjectAddressSet(address, NamespaceRelationId, namespaceId);
+			checkMembershipInCurrentExtension(&address);
+
+			/* OK to skip */
+			ereport(NOTICE,
+					(errcode(ERRCODE_DUPLICATE_SCHEMA),
+					 errmsg("schema \"%s\" already exists, skipping",
+							schemaName)));
+			return InvalidOid;
+		}
 	}
 
 	/*
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index 0960b339cab..0577184f82b 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -149,6 +149,14 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
 		RangeVarGetAndCheckCreationNamespace(seq->sequence, NoLock, &seqoid);
 		if (OidIsValid(seqoid))
 		{
+			/*
+			 * If we are in an extension script, insist that the pre-existing
+			 * object be a member of the extension, to avoid security risks.
+			 */
+			ObjectAddressSet(address, RelationRelationId, seqoid);
+			checkMembershipInCurrentExtension(&address);
+
+			/* OK to skip */
 			ereport(NOTICE,
 					(errcode(ERRCODE_DUPLICATE_TABLE),
 					 errmsg("relation \"%s\" already exists, skipping",
diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index 5678d31d0b6..409cf28a7ef 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -173,6 +173,10 @@ CreateStatistics(CreateStatsStmt *stmt)
 	{
 		if (stmt->if_not_exists)
 		{
+			/*
+			 * Since stats objects aren't members of extensions (see comments
+			 * below), no need for checkMembershipInCurrentExtension here.
+			 */
 			ereport(NOTICE,
 					(errcode(ERRCODE_DUPLICATE_OBJECT),
 					 errmsg("statistics object \"%s\" already exists, skipping",
diff --git a/src/backend/commands/view.c b/src/backend/commands/view.c
index 87ed453649b..dd7cc9703ec 100644
--- a/src/backend/commands/view.c
+++ b/src/backend/commands/view.c
@@ -205,7 +205,7 @@ DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
 		CommandCounterIncrement();
 
 		/*
-		 * Finally update the view options.
+		 * Update the view's options.
 		 *
 		 * The new options list replaces the existing options list, even if
 		 * it's empty.
@@ -218,8 +218,22 @@ DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
 		/* EventTriggerAlterTableStart called by ProcessUtilitySlow */
 		AlterTableInternal(viewOid, atcmds, true);
 
+		/*
+		 * There is very little to do here to update the view's dependencies.
+		 * Most view-level dependency relationships, such as those on the
+		 * owner, schema, and associated composite type, aren't changing.
+		 * Because we don't allow changing type or collation of an existing
+		 * view column, those dependencies of the existing columns don't
+		 * change either, while the AT_AddColumnToView machinery took care of
+		 * adding such dependencies for new view columns.  The dependencies of
+		 * the view's query could have changed arbitrarily, but that was dealt
+		 * with inside StoreViewQuery.  What remains is only to check that
+		 * view replacement is allowed when we're creating an extension.
+		 */
 		ObjectAddressSet(address, RelationRelationId, viewOid);
 
+		recordDependencyOnCurrentExtension(&address, true);
+
 		/*
 		 * Seems okay, so return the OID of the pre-existing view.
 		 */