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-rw-r--r--src/backend/optimizer/prep/prepjointree.c66
-rw-r--r--src/backend/rewrite/rewriteManip.c9
-rw-r--r--src/test/regress/expected/subselect.out29
-rw-r--r--src/test/regress/sql/subselect.sql18
4 files changed, 107 insertions, 15 deletions
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index 5482ab85a76..4195a0a84fe 100644
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -2490,14 +2490,48 @@ pullup_replace_vars_callback(Var *var,
else
wrap = false;
}
+ else if (rcon->wrap_non_vars)
+ {
+ /* Caller told us to wrap all non-Vars in a PlaceHolderVar */
+ wrap = true;
+ }
else
{
/*
- * Must wrap, either because we need a place to insert
- * varnullingrels or because caller told us to wrap
- * everything.
+ * If the node contains Var(s) or PlaceHolderVar(s) of the
+ * subquery being pulled up, and does not contain any
+ * non-strict constructs, then instead of adding a PHV on top
+ * we can add the required nullingrels to those Vars/PHVs.
+ * (This is fundamentally a generalization of the above cases
+ * for bare Vars and PHVs.)
+ *
+ * This test is somewhat expensive, but it avoids pessimizing
+ * the plan in cases where the nullingrels get removed again
+ * later by outer join reduction.
+ *
+ * This analysis could be tighter: in particular, a non-strict
+ * construct hidden within a lower-level PlaceHolderVar is not
+ * reason to add another PHV. But for now it doesn't seem
+ * worth the code to be more exact.
+ *
+ * For a LATERAL subquery, we have to check the actual var
+ * membership of the node, but if it's non-lateral then any
+ * level-zero var must belong to the subquery.
*/
- wrap = true;
+ if ((rcon->target_rte->lateral ?
+ bms_overlap(pull_varnos(rcon->root, newnode),
+ rcon->relids) :
+ contain_vars_of_level(newnode, 0)) &&
+ !contain_nonstrict_functions(newnode))
+ {
+ /* No wrap needed */
+ wrap = false;
+ }
+ else
+ {
+ /* Else wrap it in a PlaceHolderVar */
+ wrap = true;
+ }
}
if (wrap)
@@ -2518,18 +2552,14 @@ pullup_replace_vars_callback(Var *var,
}
}
- /* Must adjust varlevelsup if replaced Var is within a subquery */
- if (var->varlevelsup > 0)
- IncrementVarSublevelsUp(newnode, var->varlevelsup, 0);
-
- /* Propagate any varnullingrels into the replacement Var or PHV */
+ /* Propagate any varnullingrels into the replacement expression */
if (var->varnullingrels != NULL)
{
if (IsA(newnode, Var))
{
Var *newvar = (Var *) newnode;
- Assert(newvar->varlevelsup == var->varlevelsup);
+ Assert(newvar->varlevelsup == 0);
newvar->varnullingrels = bms_add_members(newvar->varnullingrels,
var->varnullingrels);
}
@@ -2537,14 +2567,26 @@ pullup_replace_vars_callback(Var *var,
{
PlaceHolderVar *newphv = (PlaceHolderVar *) newnode;
- Assert(newphv->phlevelsup == var->varlevelsup);
+ Assert(newphv->phlevelsup == 0);
newphv->phnullingrels = bms_add_members(newphv->phnullingrels,
var->varnullingrels);
}
else
- elog(ERROR, "failed to wrap a non-Var");
+ {
+ /* There should be lower-level Vars/PHVs we can modify */
+ newnode = add_nulling_relids(newnode,
+ NULL, /* modify all Vars/PHVs */
+ var->varnullingrels);
+ /* Assert we did put the varnullingrels into the expression */
+ Assert(bms_is_subset(var->varnullingrels,
+ pull_varnos(rcon->root, newnode)));
+ }
}
+ /* Must adjust varlevelsup if replaced Var is within a subquery */
+ if (var->varlevelsup > 0)
+ IncrementVarSublevelsUp(newnode, var->varlevelsup, 0);
+
return newnode;
}
diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
index 191f2dc0b1d..b20625fbd2b 100644
--- a/src/backend/rewrite/rewriteManip.c
+++ b/src/backend/rewrite/rewriteManip.c
@@ -1141,7 +1141,8 @@ AddInvertedQual(Query *parsetree, Node *qual)
/*
* add_nulling_relids() finds Vars and PlaceHolderVars that belong to any
* of the target_relids, and adds added_relids to their varnullingrels
- * and phnullingrels fields.
+ * and phnullingrels fields. If target_relids is NULL, all level-zero
+ * Vars and PHVs are modified.
*/
Node *
add_nulling_relids(Node *node,
@@ -1170,7 +1171,8 @@ add_nulling_relids_mutator(Node *node,
Var *var = (Var *) node;
if (var->varlevelsup == context->sublevels_up &&
- bms_is_member(var->varno, context->target_relids))
+ (context->target_relids == NULL ||
+ bms_is_member(var->varno, context->target_relids)))
{
Relids newnullingrels = bms_union(var->varnullingrels,
context->added_relids);
@@ -1188,7 +1190,8 @@ add_nulling_relids_mutator(Node *node,
PlaceHolderVar *phv = (PlaceHolderVar *) node;
if (phv->phlevelsup == context->sublevels_up &&
- bms_overlap(phv->phrels, context->target_relids))
+ (context->target_relids == NULL ||
+ bms_overlap(phv->phrels, context->target_relids)))
{
Relids newnullingrels = bms_union(phv->phnullingrels,
context->added_relids);
diff --git a/src/test/regress/expected/subselect.out b/src/test/regress/expected/subselect.out
index 9eecdc1e924..2d35de3fad6 100644
--- a/src/test/regress/expected/subselect.out
+++ b/src/test/regress/expected/subselect.out
@@ -1722,6 +1722,35 @@ fetch backward all in c1;
commit;
--
+-- Verify that we correctly flatten cases involving a subquery output
+-- expression that doesn't need to be wrapped in a PlaceHolderVar
+--
+explain (costs off)
+select tname, attname from (
+select relname::information_schema.sql_identifier as tname, * from
+ (select * from pg_class c) ss1) ss2
+ right join pg_attribute a on a.attrelid = ss2.oid
+where tname = 'tenk1' and attnum = 1;
+ QUERY PLAN
+--------------------------------------------------------------------------
+ Nested Loop
+ -> Index Scan using pg_class_relname_nsp_index on pg_class c
+ Index Cond: (relname = 'tenk1'::name)
+ -> Index Scan using pg_attribute_relid_attnum_index on pg_attribute a
+ Index Cond: ((attrelid = c.oid) AND (attnum = 1))
+(5 rows)
+
+select tname, attname from (
+select relname::information_schema.sql_identifier as tname, * from
+ (select * from pg_class c) ss1) ss2
+ right join pg_attribute a on a.attrelid = ss2.oid
+where tname = 'tenk1' and attnum = 1;
+ tname | attname
+-------+---------
+ tenk1 | unique1
+(1 row)
+
+--
-- Tests for CTE inlining behavior
--
-- Basic subquery that can be inlined
diff --git a/src/test/regress/sql/subselect.sql b/src/test/regress/sql/subselect.sql
index 75a9b718b2f..af6e157aca0 100644
--- a/src/test/regress/sql/subselect.sql
+++ b/src/test/regress/sql/subselect.sql
@@ -891,6 +891,24 @@ fetch backward all in c1;
commit;
--
+-- Verify that we correctly flatten cases involving a subquery output
+-- expression that doesn't need to be wrapped in a PlaceHolderVar
+--
+
+explain (costs off)
+select tname, attname from (
+select relname::information_schema.sql_identifier as tname, * from
+ (select * from pg_class c) ss1) ss2
+ right join pg_attribute a on a.attrelid = ss2.oid
+where tname = 'tenk1' and attnum = 1;
+
+select tname, attname from (
+select relname::information_schema.sql_identifier as tname, * from
+ (select * from pg_class c) ss1) ss2
+ right join pg_attribute a on a.attrelid = ss2.oid
+where tname = 'tenk1' and attnum = 1;
+
+--
-- Tests for CTE inlining behavior
--
generated by cgit v1.2.3 (git 2.25.1) at 2025-05-20 20:54:51 +0000