Disable FQS for cursors defined with SCROLL

When checking if a query is eligible for FQS (fast-query shipping),
disable the optimization for queries in SCROLL cursors, as FQS does
not support backward scans.

Discussion: <[email protected]>

4 files changed, 15 insertions, 14 deletions

diff --git a/src/backend/commands/portalcmds.c b/src/backend/commands/portalcmds.c
index 9fb9bf6bcd..82dfa98134 100644
--- a/src/backend/commands/portalcmds.c
+++ b/src/backend/commands/portalcmds.c
@@ -28,6 +28,7 @@
 #include "commands/portalcmds.h"
 #include "executor/executor.h"
 #include "executor/tstoreReceiver.h"
+#include "optimizer/cost.h"
 #include "rewrite/rewriteHandler.h"
 #include "tcop/pquery.h"
 #include "tcop/tcopprot.h"
diff --git a/src/backend/pgxc/plan/planner.c b/src/backend/pgxc/plan/planner.c
index ee510537b4..6f602cd7b0 100644
--- a/src/backend/pgxc/plan/planner.c
+++ b/src/backend/pgxc/plan/planner.c
@@ -62,7 +62,8 @@
 
 
 static bool contains_temp_tables(List *rtable);
-static PlannedStmt *pgxc_FQS_planner(Query *query, ParamListInfo boundParams);
+static PlannedStmt *pgxc_FQS_planner(Query *query, int cursorOptions,
+									 ParamListInfo boundParams);
 static RemoteQuery *pgxc_FQS_create_remote_plan(Query *query,
 												ExecNodes *exec_nodes,
 												bool is_exec_direct);
@@ -225,7 +226,7 @@ pgxc_planner(Query *query, int cursorOptions, ParamListInfo boundParams)
 	PlannedStmt *result;
 
 	/* see if can ship the query completely */
-	result = pgxc_FQS_planner(query, boundParams);
+	result = pgxc_FQS_planner(query, cursorOptions, boundParams);
 	if (result)
 		return result;
 
@@ -259,7 +260,7 @@ pgxc_planner(Query *query, int cursorOptions, ParamListInfo boundParams)
  * fqs in the name of function is acronym for fast query shipping.
  */
 static PlannedStmt *
-pgxc_FQS_planner(Query *query, ParamListInfo boundParams)
+pgxc_FQS_planner(Query *query, int cursorOptions, ParamListInfo boundParams)
 {
 	PlannedStmt		*result;
 	PlannerGlobal	*glob;
@@ -271,9 +272,8 @@ pgxc_FQS_planner(Query *query, ParamListInfo boundParams)
 	if (!enable_fast_query_shipping)
 		return NULL;
 
-	/* Do not FQS cursor statements */
-	if (query->utilityStmt &&
-		IsA(query->utilityStmt, DeclareCursorStmt))
+	/* Do not FQS cursor statements that require backward scrolling */
+	if (cursorOptions & CURSOR_OPT_SCROLL)
 		return NULL;
 
 	/* Do not FQS EXEC DIRECT statements */
diff --git a/src/test/regress/expected/limit.out b/src/test/regress/expected/limit.out
index 0edbb85afd..0af7e2f0c9 100644
--- a/src/test/regress/expected/limit.out
+++ b/src/test/regress/expected/limit.out
@@ -132,7 +132,7 @@ select * from int8_tbl offset (case when random() < 0.5 then null::bigint end);
 
 -- Test assorted cases involving backwards fetch from a LIMIT plan node
 begin;
-declare c1 cursor for select * from int8_tbl limit 10;
+declare c1 scroll cursor for select * from int8_tbl limit 10;
 fetch all in c1;
         q1        |        q2         
 ------------------+-------------------
@@ -178,7 +178,7 @@ fetch all in c1;
  4567890123456789 | -4567890123456789
 (5 rows)
 
-declare c2 cursor for select * from int8_tbl limit 3;
+declare c2 scroll cursor for select * from int8_tbl limit 3;
 fetch all in c2;
         q1        |        q2        
 ------------------+------------------
@@ -218,7 +218,7 @@ fetch all in c2;
  4567890123456789 |              123
 (3 rows)
 
-declare c3 cursor for select * from int8_tbl offset 3;
+declare c3 scroll cursor for select * from int8_tbl offset 3;
 fetch all in c3;
         q1        |        q2         
 ------------------+-------------------
@@ -255,7 +255,7 @@ fetch all in c3;
  4567890123456789 | -4567890123456789
 (2 rows)
 
-declare c4 cursor for select * from int8_tbl offset 10;
+declare c4 scroll cursor for select * from int8_tbl offset 10;
 fetch all in c4;
  q1 | q2 
 ----+----
diff --git a/src/test/regress/sql/limit.sql b/src/test/regress/sql/limit.sql
index 2a313d80ca..f9b2fe5c00 100644
--- a/src/test/regress/sql/limit.sql
+++ b/src/test/regress/sql/limit.sql
@@ -39,7 +39,7 @@ select * from int8_tbl offset (case when random() < 0.5 then null::bigint end);
 -- Test assorted cases involving backwards fetch from a LIMIT plan node
 begin;
 
-declare c1 cursor for select * from int8_tbl limit 10;
+declare c1 scroll cursor for select * from int8_tbl limit 10;
 fetch all in c1;
 fetch 1 in c1;
 fetch backward 1 in c1;
@@ -47,7 +47,7 @@ fetch backward all in c1;
 fetch backward 1 in c1;
 fetch all in c1;
 
-declare c2 cursor for select * from int8_tbl limit 3;
+declare c2 scroll cursor for select * from int8_tbl limit 3;
 fetch all in c2;
 fetch 1 in c2;
 fetch backward 1 in c2;
@@ -55,7 +55,7 @@ fetch backward all in c2;
 fetch backward 1 in c2;
 fetch all in c2;
 
-declare c3 cursor for select * from int8_tbl offset 3;
+declare c3 scroll cursor for select * from int8_tbl offset 3;
 fetch all in c3;
 fetch 1 in c3;
 fetch backward 1 in c3;
@@ -63,7 +63,7 @@ fetch backward all in c3;
 fetch backward 1 in c3;
 fetch all in c3;
 
-declare c4 cursor for select * from int8_tbl offset 10;
+declare c4 scroll cursor for select * from int8_tbl offset 10;
 fetch all in c4;
 fetch 1 in c4;
 fetch backward 1 in c4;