Fix pg_prepared_statements.result_types for DML statements

Amendment to 84ad713cf85aeffee5dd39f62d49a1b9e34632da: Not all
prepared statements have a result descriptor.  As currently coded,
this would crash when reading pg_prepared_statements.  Make those
cases return null for result_types instead.  Also add a test case for
it.

1 files changed, 14 insertions, 6 deletions

diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index d1deb97fffb..2333aae4673 100644
--- a/src/backend/commands/prepare.c
+++ b/src/backend/commands/prepare.c
@@ -684,15 +684,10 @@ pg_prepared_statement(PG_FUNCTION_ARGS)
 		while ((prep_stmt = hash_seq_search(&hash_seq)) != NULL)
 		{
 			TupleDesc	result_desc;
-			Oid		   *result_types;
 			Datum		values[8];
 			bool		nulls[8];
 
 			result_desc = prep_stmt->plansource->resultDesc;
-			result_types = (Oid *) palloc(result_desc->natts * sizeof(Oid));
-
-			for (int i = 0; i < result_desc->natts; i++)
-				result_types[i] = result_desc->attrs[i].atttypid;
 
 			MemSet(nulls, 0, sizeof(nulls));
 
@@ -701,7 +696,20 @@ pg_prepared_statement(PG_FUNCTION_ARGS)
 			values[2] = TimestampTzGetDatum(prep_stmt->prepare_time);
 			values[3] = build_regtype_array(prep_stmt->plansource->param_types,
 											prep_stmt->plansource->num_params);
-			values[4] = build_regtype_array(result_types, result_desc->natts);
+			if (result_desc)
+			{
+				Oid		   *result_types;
+
+				result_types = (Oid *) palloc(result_desc->natts * sizeof(Oid));
+				for (int i = 0; i < result_desc->natts; i++)
+					result_types[i] = result_desc->attrs[i].atttypid;
+				values[4] = build_regtype_array(result_types, result_desc->natts);
+			}
+			else
+			{
+				/* no result descriptor (for example, DML statement) */
+				nulls[4] = true;
+			}
 			values[5] = BoolGetDatum(prep_stmt->from_sql);
 			values[6] = Int64GetDatumFast(prep_stmt->plansource->num_generic_plans);
 			values[7] = Int64GetDatumFast(prep_stmt->plansource->num_custom_plans);