Don't copyObject into the wrong memory context

utilityStmt sometimes (such as when it's inside of a plpgsql function)
comes from a cached plan, which is kept in a child of the
CacheMemoryContext. When we naively call copyObject we're copying it into
a statement-local context, which corrupts the cached plan when it's
thrown away.

src/backend/distributed/executor/multi_utility.c

@@ -62,6 +62,7 @@
 #include "foreign/foreign.h"
 #include "lib/stringinfo.h"
 #include "nodes/bitmapset.h"
+#include "nodes/memnodes.h"
 #include "nodes/nodes.h"
 #include "nodes/params.h"
 #include "nodes/parsenodes.h"
@@ -311,12 +312,17 @@ multi_ProcessUtility(PlannedStmt *pstmt,
 
 	if (IsA(parsetree, CopyStmt))
 	{
-		/* copy parse tree since we might scribble on it to fix the schema name */
-		parsetree = copyObject(parsetree);
+		MemoryContext planContext = GetMemoryChunkContext(parsetree);
+		MemoryContext previousContext;
 
+		parsetree = copyObject(parsetree);
 		parsetree = ProcessCopyStmt((CopyStmt *) parsetree, completionTag,
 									&commandMustRunAsOwner);
 
+		previousContext = MemoryContextSwitchTo(planContext);
+		parsetree = copyObject(parsetree);
+		MemoryContextSwitchTo(previousContext);
+
 		if (parsetree == NULL)
 		{
 			return;

src/test/regress/expected/multi_prepare_plsql.out

@@ -1233,9 +1233,31 @@ SELECT copy_in_plpgsql();
 
 (1 row)
 
+-- test prepared COPY on a non-distributed table
+CREATE TABLE local_ddl (x int);
+CREATE OR REPLACE FUNCTION local_copy_in_plpgsql()
+RETURNS VOID  AS
+$BODY$
+BEGIN
+    COPY local_ddl (x) FROM PROGRAM 'echo 1' WITH CSV;
+END;
+$BODY$ LANGUAGE plpgsql;
+SELECT local_copy_in_plpgsql();
+ local_copy_in_plpgsql 
+-----------------------
+
+(1 row)
+
+SELECT local_copy_in_plpgsql();
+ local_copy_in_plpgsql 
+-----------------------
+
+(1 row)
+
 DROP FUNCTION ddl_in_plpgsql();
 DROP FUNCTION copy_in_plpgsql();
 DROP TABLE prepare_ddl;
+DROP TABLE local_ddl;
 -- clean-up functions
 DROP FUNCTION plpgsql_test_1();
 DROP FUNCTION plpgsql_test_2();

src/test/regress/sql/multi_prepare_plsql.sql

@@ -563,9 +563,24 @@ $BODY$ LANGUAGE plpgsql;
 SELECT copy_in_plpgsql();
 SELECT copy_in_plpgsql();
 
+-- test prepared COPY on a non-distributed table
+CREATE TABLE local_ddl (x int);
+
+CREATE OR REPLACE FUNCTION local_copy_in_plpgsql()
+RETURNS VOID  AS
+$BODY$
+BEGIN
+    COPY local_ddl (x) FROM PROGRAM 'echo 1' WITH CSV;
+END;
+$BODY$ LANGUAGE plpgsql;
+
+SELECT local_copy_in_plpgsql();
+SELECT local_copy_in_plpgsql();
+
 DROP FUNCTION ddl_in_plpgsql();
 DROP FUNCTION copy_in_plpgsql();
 DROP TABLE prepare_ddl;
+DROP TABLE local_ddl;
 
 -- clean-up functions
 DROP FUNCTION plpgsql_test_1();