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Don't constrain self-join removal due to PHVs

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Self-join removal appears to be safe to apply with placeholder variables
as long as we handle PlaceHolderVar in replace_varno_walker() and replace
relid in phinfo->ph_lateral.

Discussion: https://postgr.es/m/18187-831da249cbd2ff8e%40postgresql.org
Author: Richard Guo
Reviewed-by: Andrei Lepikhov
This commit is contained in:
Alexander Korotkov
2023-12-25 01:24:25 +02:00
parent 8a8ed916f7
commit b5fb6736ed
3 changed files with 39 additions and 28 deletions
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18
src/backend/optimizer/plan/analyzejoins.c
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@@ -453,7 +453,7 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
Assert(!bms_is_member(relid, phinfo->ph_lateral));
Assert(sjinfo == NULL || !bms_is_member(relid, phinfo->ph_lateral));
if (bms_is_subset(phinfo->ph_needed, joinrelids) &&
bms_is_member(relid, phinfo->ph_eval_at) &&
!bms_is_member(ojrelid, phinfo->ph_eval_at))
@@ -472,6 +472,8 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
phinfo->ph_needed = replace_relid(phinfo->ph_needed, relid, subst);
phinfo->ph_needed = replace_relid(phinfo->ph_needed, ojrelid, subst);
/* ph_needed might or might not become empty */
phinfo->ph_lateral = replace_relid(phinfo->ph_lateral, relid, subst);
/* ph_lateral might or might not be empty */
phv->phrels = replace_relid(phv->phrels, relid, subst);
phv->phrels = replace_relid(phv->phrels, ojrelid, subst);
Assert(!bms_is_empty(phv->phrels));
@@ -2115,20 +2117,8 @@ remove_self_joins_one_group(PlannerInfo *root, Relids relids)
joinrelids = bms_add_member(joinrelids, k);
/*
* Be safe to do not remove tables participated in complicated PH
* PHVs should not impose any constraints on removing self joins.
*/
foreach(lc, root->placeholder_list)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
/* there isn't any other place to eval PHV */
if (bms_is_subset(phinfo->ph_eval_at, joinrelids) ||
bms_is_subset(phinfo->ph_needed, joinrelids) ||
bms_is_member(r, phinfo->ph_lateral))
break;
}
if (lc)
continue;
/*
* At this stage, joininfo lists of inner and outer can contain