Fix missed step in removal of useless RESULT RTEs in the planner.

tglsfdc · tglsfdc · commit e98c900993e8 · 2020-12-05T16:16:13.000-05:00
Commit 4be058f forgot that the append_rel_list would already be populated at the time we remove useless result RTEs, and it might contain PlaceHolderVars that need to be adjusted like the ones in the main parse tree. This could lead to "no relation entry for relid N" failures later on, when the planner tries to do something with an unadjusted PHV. Per report from Tom Ellis. Back-patch to v12 where the bug came in. Discussion: https://postgr.es/m/20201205173056.GF30712@cloudinit-builder
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
@@ -3256,6 +3256,7 @@ remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc)
 		subrelids = get_relids_in_jointree(newjtloc, false);
 		Assert(!bms_is_empty(subrelids));
 		substitute_phv_relids((Node *) root->parse, varno, subrelids);
+		fix_append_rel_relids(root->append_rel_list, varno, subrelids);
 	}
 
 	/*
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
@@ -3333,6 +3333,42 @@ select * from
  1 | 2 | 2
 (1 row)
 
+-- Test proper handling of appendrel PHVs during useless-RTE removal
+explain (costs off)
+select * from
+  (select 0 as z) as t1
+  left join
+  (select true as a) as t2
+  on true,
+  lateral (select true as b
+           union all
+           select a as b) as t3
+where b;
+              QUERY PLAN               
+---------------------------------------
+ Nested Loop
+   ->  Result
+   ->  Append
+         ->  Result
+         ->  Result
+               One-Time Filter: (true)
+(6 rows)
+
+select * from
+  (select 0 as z) as t1
+  left join
+  (select true as a) as t2
+  on true,
+  lateral (select true as b
+           union all
+           select a as b) as t3
+where b;
+ z | a | b 
+---+---+---
+ 0 | t | t
+ 0 | t | t
+(2 rows)
+
 --
 -- test inlining of immutable functions
 --
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
@@ -1056,6 +1056,28 @@ select * from
   (select 1 as x) ss1 left join (select 2 as y) ss2 on (true),
   lateral (select ss2.y as z limit 1) ss3;
 
+-- Test proper handling of appendrel PHVs during useless-RTE removal
+explain (costs off)
+select * from
+  (select 0 as z) as t1
+  left join
+  (select true as a) as t2
+  on true,
+  lateral (select true as b
+           union all
+           select a as b) as t3
+where b;
+
+select * from
+  (select 0 as z) as t1
+  left join
+  (select true as a) as t2
+  on true,
+  lateral (select true as b
+           union all
+           select a as b) as t3
+where b;
+
 --
 -- test inlining of immutable functions
 --

Original file line number	Diff line number	Diff line change
`@@ -3256,6 +3256,7 @@ remove_result_refs(PlannerInfo root, int varno, Node newjtloc)`
`3256`	`3256`	`subrelids = get_relids_in_jointree(newjtloc, false);`
`3257`	`3257`	`Assert(!bms_is_empty(subrelids));`
`3258`	`3258`	`substitute_phv_relids((Node *) root->parse, varno, subrelids);`
	`3259`	`+ fix_append_rel_relids(root->append_rel_list, varno, subrelids);`
`3259`	`3260`	`}`
`3260`	`3261`
`3261`	`3262`	`/*`