Don't change query tree of DDL commands

Based on 853f07dd33

src/backend/distributed/executor/multi_utility.c

@@ -227,6 +227,9 @@ multi_ProcessUtility(Node *parsetree,
 
 	if (IsA(parsetree, CopyStmt))
 	{
+		/* copy parse tree since we might scribble on it to fix the schema name */
+		parsetree = copyObject(parsetree);
+
 		parsetree = ProcessCopyStmt((CopyStmt *) parsetree, completionTag,
 									&commandMustRunAsOwner);
 
@@ -261,6 +264,8 @@ multi_ProcessUtility(Node *parsetree,
 
 		if (IsA(parsetree, IndexStmt))
 		{
+			/* copy parse tree since we might scribble on it to fix the schema name */
+			parsetree = copyObject(parsetree);
 			parsetree = ProcessIndexStmt((IndexStmt *) parsetree, queryString,
 										 isTopLevel);
 		}
@@ -698,7 +703,13 @@ ProcessIndexStmt(IndexStmt *createIndexStatement, const char *createIndexCommand
 
 		isDistributedRelation = IsDistributedTable(relationId);
 
-		/* ensure future lookups hit the same relation */
+		/*
+		 * Before we do any further processing, fix the schema name to make sure
+		 * that a (distributed) table with the same name does not appear on the
+		 * search path in front of the current schema. We do this even if the
+		 * table is not distributed, since a distributed table may appear on the
+		 * search path by the time postgres starts processing this statement.
+		 */
 		namespaceName = get_namespace_name(RelationGetNamespace(relation));
 		createIndexStatement->relation->schemaname = namespaceName;
 

src/test/regress/expected/multi_prepare_plsql.out

@@ -1106,6 +1106,58 @@ BEGIN
 END;
 $$;
 DROP TABLE execute_parameter_test;
+-- test prepared DDL, mainly to verify we don't mess up the query tree
+SET citus.multi_shard_commit_protocol TO '2pc';
+CREATE TABLE prepare_ddl (x int, y int);
+SELECT create_distributed_table('prepare_ddl', 'x');
+ create_distributed_table 
+--------------------------
+ 
+(1 row)
+
+CREATE OR REPLACE FUNCTION ddl_in_plpgsql()
+RETURNS VOID  AS
+$BODY$
+BEGIN
+    CREATE INDEX prepared_index ON public.prepare_ddl(x);
+    DROP INDEX prepared_index;
+END;
+$BODY$ LANGUAGE plpgsql;
+SELECT ddl_in_plpgsql();
+ ddl_in_plpgsql 
+----------------
+ 
+(1 row)
+
+SELECT ddl_in_plpgsql();
+ ddl_in_plpgsql 
+----------------
+ 
+(1 row)
+
+-- test prepared COPY
+CREATE OR REPLACE FUNCTION copy_in_plpgsql()
+RETURNS VOID  AS
+$BODY$
+BEGIN
+    COPY prepare_ddl (x) FROM PROGRAM 'echo 1' WITH CSV;
+END;
+$BODY$ LANGUAGE plpgsql;
+SELECT copy_in_plpgsql();
+ copy_in_plpgsql 
+-----------------
+ 
+(1 row)
+
+SELECT copy_in_plpgsql();
+ copy_in_plpgsql 
+-----------------
+ 
+(1 row)
+
+DROP FUNCTION ddl_in_plpgsql();
+DROP FUNCTION copy_in_plpgsql();
+DROP TABLE prepare_ddl;
 -- clean-up functions
 DROP FUNCTION plpgsql_test_1();
 DROP FUNCTION plpgsql_test_2();

src/test/regress/sql/multi_prepare_plsql.sql

@@ -497,6 +497,39 @@ END;
 $$;
 DROP TABLE execute_parameter_test;
 
+-- test prepared DDL, mainly to verify we don't mess up the query tree
+SET citus.multi_shard_commit_protocol TO '2pc';
+CREATE TABLE prepare_ddl (x int, y int);
+SELECT create_distributed_table('prepare_ddl', 'x');
+
+CREATE OR REPLACE FUNCTION ddl_in_plpgsql()
+RETURNS VOID  AS
+$BODY$
+BEGIN
+    CREATE INDEX prepared_index ON public.prepare_ddl(x);
+    DROP INDEX prepared_index;
+END;
+$BODY$ LANGUAGE plpgsql;
+
+SELECT ddl_in_plpgsql();
+SELECT ddl_in_plpgsql();
+
+-- test prepared COPY
+CREATE OR REPLACE FUNCTION copy_in_plpgsql()
+RETURNS VOID  AS
+$BODY$
+BEGIN
+    COPY prepare_ddl (x) FROM PROGRAM 'echo 1' WITH CSV;
+END;
+$BODY$ LANGUAGE plpgsql;
+
+SELECT copy_in_plpgsql();
+SELECT copy_in_plpgsql();
+
+DROP FUNCTION ddl_in_plpgsql();
+DROP FUNCTION copy_in_plpgsql();
+DROP TABLE prepare_ddl;
+
 -- clean-up functions
 DROP FUNCTION plpgsql_test_1();
 DROP FUNCTION plpgsql_test_2();