Add resource group bypassing for GUC rollback

src/backend/tcop/postgres.c

@@ -79,6 +79,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
+#include "utils/resgroup.h"
 #include "utils/snapmgr.h"
 #include "utils/timeout.h"
 #include "utils/timestamp.h"
@@ -1569,10 +1570,29 @@ CheckDebugDtmActionSqlCommandTag(const char *sqlCommandTag)
 static void
 restore_guc_to_QE(void )
 {
+	ListCell 	*lc;
+	bool		saved_resgroup_bypass = gp_resource_group_bypass;
+
 	Assert(Gp_role == GP_ROLE_DISPATCH && gp_guc_restore_list);
-	ListCell *lc;
 
-	start_xact_command();
+	/* debug_query_string (which is used to make a bypass decision) is
+	 * unavailable in this context meaning that we won't bypass resource
+	 * group here.
+	 * To forse the bypass we temporarily set gp_resource_group_bypass manually.
+	 *
+	 */
+	PG_TRY();
+	{
+		gp_resource_group_bypass = true;
+		start_xact_command();
+	}
+	PG_CATCH();
+	{
+		gp_resource_group_bypass = saved_resgroup_bypass;
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+	gp_resource_group_bypass = saved_resgroup_bypass;
 
 	foreach(lc, gp_guc_restore_list)
 	{

src/test/isolation2/input/resgroup/resgroup_bypass.source

@@ -76,6 +76,11 @@ ALTER RESOURCE GROUP rg_bypass_test set concurrency 1;
 ALTER RESOURCE GROUP rg_bypass_test set concurrency 0;
 61: SET enable_hashagg to on;
 61: SHOW enable_hashagg;
+-- Roll back a GUC change in one query message; restoration must not wait
+-- for a resource-group slot (concurrency is still zero).
+61: SET DateStyle = 'ISO, MDY';
+61: SET DateStyle = 'SQL, DMY'; SET work_mem = 'invalid';
+61: SHOW DateStyle;
 61: invalid_syntax;
 61q:
 

src/test/isolation2/output/resgroup/resgroup_bypass.source

@@ -74,6 +74,17 @@ SET
 ----------------
  on             
 (1 row)
+-- Roll back a GUC change in one query message; restoration must not wait
+-- for a resource-group slot (concurrency is still zero).
+61: SET DateStyle = 'ISO, MDY';
+SET
+61: SET DateStyle = 'SQL, DMY'; SET work_mem = 'invalid';
+ERROR:  invalid value for parameter "work_mem": "invalid"
+61: SHOW DateStyle;
+ DateStyle 
+-----------
+ ISO, MDY  
+(1 row)
 61: invalid_syntax;
 ERROR:  syntax error at or near "invalid_syntax"
 LINE 1: invalid_syntax;