Dont pullup correlated subqueries with limit/offset clause

Queries in which there is a IN clause on top of a correlated subquery
containing limit/offset clause, planner tries to identify if the IN clause can
be converted to a join in convert_IN_to_join() and creates a RTE
for the join if its possible and does not consider limit/offset clause
while making a decision. However, later in pull_up_subqueries(),
check enforced by is_simple_subquery causes the subquery containing limit/offset
clauses to be not pulled up. This inconsistency causes a plan to be
generated with a param, however, with no corresponding subplan.

The patch fixes the issues by adding the relevant checks in
convert_IN_to_join() to identify if the subquery is
correlated and contains limit/offset clause, in such cases the sublink
will not be converted to a join and a plan with subplan will be created.

src/backend/optimizer/plan/subselect.c

@@ -40,6 +40,7 @@
 #include "cdb/cdbsubselect.h"
 #include "cdb/cdbvars.h"
 
+extern bool is_simple_subquery(PlannerInfo *root, Query *subquery);
 
 typedef struct convert_testexpr_context
 {
@@ -1105,13 +1106,7 @@ convert_IN_to_join(PlannerInfo *root, List **rtrlist_inout, SubLink *sublink)
 		/*
 		 * Under certain conditions, we cannot pull up the subquery as a join.
 		 */
-    	if (subselect->hasAggs
-    			|| (subselect->jointree->fromlist == NULL)
-    			|| subselect->havingQual
-    			|| subselect->groupClause
-    			|| subselect->hasWindFuncs
-    			|| subselect->distinctClause
-    			|| subselect->setOperations)
+    	if (!is_simple_subquery(root, subselect))
     		return (Node *) sublink;
     	
 		/*

src/test/regress/expected/subselect_gp.out

@@ -1110,6 +1110,59 @@ where t1.a = foo.a;
 ---+---
 (0 rows)
 
+---
+--- Correlated subqueries with limit/offset clause must not be pulled up as join
+---
+insert into t1 values (1);
+insert into t2 values (1);
+explain select 1 from t1 where a in (select b from t2 where a = 1 limit 1);
+                                                        QUERY PLAN                                                         
+---------------------------------------------------------------------------------------------------------------------------
+ Gather Motion 3:1  (slice2; segments: 3)  (cost=0.00..1.53 rows=1 width=0)
+   ->  Seq Scan on t1  (cost=0.00..1.53 rows=1 width=0)
+         Filter: (subplan)
+         SubPlan 1
+           ->  Limit  (cost=0.00..1.03 rows=1 width=4)
+                 ->  Limit  (cost=0.00..1.01 rows=1 width=4)
+                       ->  Result  (cost=0.00..1.01 rows=1 width=4)
+                             One-Time Filter: $0 = 1
+                             ->  Result  (cost=1.01..1.02 rows=1 width=4)
+                                   ->  Materialize  (cost=1.01..1.02 rows=1 width=4)
+                                         ->  Broadcast Motion 3:3  (slice1; segments: 3)  (cost=0.00..1.01 rows=1 width=4)
+                                               ->  Seq Scan on t2  (cost=0.00..1.01 rows=1 width=4)
+ Settings:  optimizer=off; optimizer_nestloop_factor=1; optimizer_segments=3
+ Optimizer status: legacy query optimizer
+(14 rows)
+
+explain select 1 from t1 where a in (select b from t2 where a = 1 offset 1);
+                                                     QUERY PLAN                                                      
+---------------------------------------------------------------------------------------------------------------------
+ Gather Motion 3:1  (slice2; segments: 3)  (cost=0.00..2.05 rows=1 width=0)
+   ->  Seq Scan on t1  (cost=0.00..2.05 rows=1 width=0)
+         Filter: (subplan)
+         SubPlan 1
+           ->  Limit  (cost=1.03..1.03 rows=1 width=4)
+                 ->  Result  (cost=0.00..1.01 rows=1 width=4)
+                       One-Time Filter: $0 = 1
+                       ->  Result  (cost=1.01..1.02 rows=1 width=4)
+                             ->  Materialize  (cost=1.01..1.02 rows=1 width=4)
+                                   ->  Broadcast Motion 3:3  (slice1; segments: 3)  (cost=0.00..1.01 rows=1 width=4)
+                                         ->  Seq Scan on t2  (cost=0.00..1.01 rows=1 width=4)
+ Settings:  optimizer=off; optimizer_nestloop_factor=1; optimizer_segments=3
+ Optimizer status: legacy query optimizer
+(13 rows)
+
+select 1 from t1 where a in (select b from t2 where a = 1 limit 1);
+ ?column? 
+----------
+        1
+(1 row)
+
+select 1 from t1 where a in (select b from t2 where a = 1 offset 1);
+ ?column? 
+----------
+(0 rows)
+
 drop table if exists t1;
 drop table if exists t2;
 --

src/test/regress/expected/subselect_gp_optimizer.out

@@ -1090,6 +1090,60 @@ where t1.a = foo.a;
 ---+---
 (0 rows)
 
+---
+--- Correlated subqueries with limit/offset clause must not be pulled up as join
+---
+insert into t1 values (1);
+insert into t2 values (1);
+explain select 1 from t1 where a in (select b from t2 where a = 1 limit 1);
+                                                  QUERY PLAN
+--------------------------------------------------------------------------------------------------------------
+ Result  (cost=0.00..1293.00 rows=1 width=4)
+   ->  Result  (cost=0.00..1293.00 rows=1 width=1)
+         Filter: (subplan)
+         ->  Gather Motion 3:1  (slice1; segments: 3)  (cost=0.00..431.00 rows=1 width=4)
+               ->  Table Scan on t1  (cost=0.00..431.00 rows=1 width=4)
+         SubPlan 1
+           ->  Limit  (cost=0.00..431.00 rows=1 width=4)
+                 ->  Result  (cost=0.00..431.00 rows=1 width=4)
+                       Filter: $1 = 1
+                       ->  Materialize  (cost=0.00..431.00 rows=1 width=4)
+                             ->  Gather Motion 3:1  (slice2; segments: 3)  (cost=0.00..431.00 rows=1 width=4)
+                                   ->  Table Scan on t2  (cost=0.00..431.00 rows=1 width=4)
+ Settings:  optimizer=on; optimizer_nestloop_factor=1; optimizer_segments=3
+ Optimizer status: PQO version 2.39.2
+(14 rows)
+
+explain select 1 from t1 where a in (select b from t2 where a = 1 offset 1);
+                                                  QUERY PLAN
+--------------------------------------------------------------------------------------------------------------
+ Result  (cost=0.00..1293.00 rows=1 width=4)
+   ->  Result  (cost=0.00..1293.00 rows=1 width=1)
+         Filter: (subplan)
+         ->  Gather Motion 3:1  (slice1; segments: 3)  (cost=0.00..431.00 rows=1 width=4)
+               ->  Table Scan on t1  (cost=0.00..431.00 rows=1 width=4)
+         SubPlan 1
+           ->  Limit  (cost=0.00..431.00 rows=1 width=4)
+                 ->  Result  (cost=0.00..431.00 rows=1 width=4)
+                       Filter: $1 = 1
+                       ->  Materialize  (cost=0.00..431.00 rows=1 width=4)
+                             ->  Gather Motion 3:1  (slice2; segments: 3)  (cost=0.00..431.00 rows=1 width=4)
+                                   ->  Table Scan on t2  (cost=0.00..431.00 rows=1 width=4)
+ Settings:  optimizer=on; optimizer_nestloop_factor=1; optimizer_segments=3
+ Optimizer status: PQO version 2.39.2
+(14 rows)
+
+select 1 from t1 where a in (select b from t2 where a = 1 limit 1);
+ ?column?
+----------
+        1
+(1 row)
+
+select 1 from t1 where a in (select b from t2 where a = 1 offset 1);
+ ?column?
+----------
+(0 rows)
+
 drop table if exists t1;
 drop table if exists t2;
 --

src/test/regress/sql/subselect_gp.sql

@@ -460,6 +460,16 @@ select * from t1,
 (select * from t1 where a=1 and a=2 and a > (select t2.b from t2)) foo
 where t1.a = foo.a;
 
+---
+--- Correlated subqueries with limit/offset clause must not be pulled up as join
+---
+insert into t1 values (1);
+insert into t2 values (1);
+explain select 1 from t1 where a in (select b from t2 where a = 1 limit 1);
+explain select 1 from t1 where a in (select b from t2 where a = 1 offset 1);
+select 1 from t1 where a in (select b from t2 where a = 1 limit 1);
+select 1 from t1 where a in (select b from t2 where a = 1 offset 1);
+
 drop table if exists t1;
 drop table if exists t2;