Fix EvalPlanQualStart to handle partitioned result rels correctly.

The es_root_result_relations array needs to be shallow-copied in the
same way as the main es_result_relations array, else EPQ rechecks on
partitioned result relations fail, as seen in bug #15677 from
Norbert Benkocs.

Amit Langote, isolation test case added by me

Discussion: https://postgr.es/m/15677-0bf089579b4cd02d@postgresql.org
Discussion: https://postgr.es/m/19321.1554567786@sss.pgh.pa.us

src/backend/executor/execMain.c

@@ -2779,7 +2779,7 @@ EvalPlanQualStart(EPQState *epqstate, EState *parentestate, Plan *planTree)
 	 * es_param_exec_vals, etc.
 	 *
 	 * The ResultRelInfo array management is trickier than it looks.  We
-	 * create a fresh array for the child but copy all the content from the
+	 * create fresh arrays for the child but copy all the content from the
 	 * parent.  This is because it's okay for the child to share any
 	 * per-relation state the parent has already created --- but if the child
 	 * sets up any ResultRelInfo fields, such as its own junkfilter, that
@@ -2800,6 +2800,7 @@ EvalPlanQualStart(EPQState *epqstate, EState *parentestate, Plan *planTree)
 	if (parentestate->es_num_result_relations > 0)
 	{
 		int			numResultRelations = parentestate->es_num_result_relations;
+		int			numRootResultRels = parentestate->es_num_root_result_relations;
 		ResultRelInfo *resultRelInfos;
 
 		resultRelInfos = (ResultRelInfo *)
@@ -2808,6 +2809,17 @@ EvalPlanQualStart(EPQState *epqstate, EState *parentestate, Plan *planTree)
 			   numResultRelations * sizeof(ResultRelInfo));
 		estate->es_result_relations = resultRelInfos;
 		estate->es_num_result_relations = numResultRelations;
+
+		/* Also transfer partitioned root result relations. */
+		if (numRootResultRels > 0)
+		{
+			resultRelInfos = (ResultRelInfo *)
+				palloc(numRootResultRels * sizeof(ResultRelInfo));
+			memcpy(resultRelInfos, parentestate->es_root_result_relations,
+				   numRootResultRels * sizeof(ResultRelInfo));
+			estate->es_root_result_relations = resultRelInfos;
+			estate->es_num_root_result_relations = numRootResultRels;
+		}
 	}
 	/* es_result_relation_info must NOT be copied */
 	/* es_trig_target_relations must NOT be copied */

src/test/isolation/expected/eval-plan-qual.out

@@ -629,3 +629,15 @@ step multireadwcte: <... completed>
 subid          id             
 
 1              1              
+
+starting permutation: simplepartupdate complexpartupdate c1 c2
+step simplepartupdate: 
+	update parttbl set a = a;
+
+step complexpartupdate: 
+	with u as (update parttbl set a = a returning parttbl.*)
+	update parttbl set a = u.a from u;
+ <waiting ...>
+step c1: COMMIT;
+step complexpartupdate: <... completed>
+step c2: COMMIT;

src/test/isolation/specs/eval-plan-qual.spec

@@ -32,6 +32,10 @@ setup
 
  CREATE TABLE jointest AS SELECT generate_series(1,10) AS id, 0 AS data;
  CREATE INDEX ON jointest(id);
+
+ CREATE TABLE parttbl (a int) PARTITION BY LIST (a);
+ CREATE TABLE parttbl1 PARTITION OF parttbl FOR VALUES IN (1);
+ INSERT INTO parttbl VALUES (1);
 }
 
 teardown
@@ -41,6 +45,7 @@ teardown
  DROP TABLE accounts_ext;
  DROP TABLE p CASCADE;
  DROP TABLE table_a, table_b, jointest;
+ DROP TABLE parttbl;
 }
 
 session "s1"
@@ -137,6 +142,12 @@ step "selectresultforupdate"	{
 	  where jt.id = y for update of jt, ss1, ss2;
 }
 
+# test for EPQ on a partitioned result table
+
+step "simplepartupdate"	{
+	update parttbl set a = a;
+}
+
 
 session "s2"
 setup		{ BEGIN ISOLATION LEVEL READ COMMITTED; }
@@ -174,6 +185,10 @@ step "updateforcip3"	{
 }
 step "wrtwcte"	{ UPDATE table_a SET value = 'tableAValue2' WHERE id = 1; }
 step "wrjt"	{ UPDATE jointest SET data = 42 WHERE id = 7; }
+step "complexpartupdate"	{
+	with u as (update parttbl set a = a returning parttbl.*)
+	update parttbl set a = u.a from u;
+}
 
 # Use writable CTEs to create self-updated rows, that then are
 # (updated|deleted). The *fail versions of the tests additionally
@@ -261,3 +276,5 @@ permutation "wrtwcte" "readwcte" "c1" "c2"
 permutation "wrjt" "selectjoinforupdate" "c2" "c1"
 permutation "wrjt" "selectresultforupdate" "c2" "c1"
 permutation "wrtwcte" "multireadwcte" "c1" "c2"
+
+permutation "simplepartupdate" "complexpartupdate" "c1" "c2"