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Further tighten nullingrel marking rules in build_joinrel_tlist().

Wed, 8 Feb 2023 19:45:36 +0000 (14:45 -0500)

The code I added in fee7b77b9 could misbehave if commute_above_r
contains multiple relids. While adding too many relids here is
probably harmless (pre-fee7b77b9, we did it all the time), it's
not very expensive to be accurate: we just have to intersect
commute_above_r with the join's relids.

Discussion: https://postgr.es/m/17781-c0405c8b3cd5e072@postgresql.org

src/backend/optimizer/util/relnode.c patch | blob | blame | history

diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c

index 29da78b62ef89943c18181ac0fd366f136bac61f..a70a16238a8526b5a306053beb874543301aa08f 100644 (file)

--- a/src/backend/optimizer/util/relnode.c

+++ b/src/backend/optimizer/util/relnode.c

@@ -1051,9 +1051,9 @@ min_join_parameterization(PlannerInfo *root,

* A leftjoin (B leftjoin C on (Pbc)) on (Pab)

* Here the now-upper A/B join must not mark C columns as nulled by itself.

- * Second, if sjinfo->commute_above_r is already part of the joinrel then

- * it is added to the nulling bitmaps of nullable Vars. This takes care of

- * the reverse case where we implement

+ * Second, any relid in sjinfo->commute_above_r that is already part of

+ * the joinrel is added to the nulling bitmaps of nullable Vars and PHVs.

+ * This takes care of the reverse case where we implement

* A leftjoin (B leftjoin C on (Pbc)) on (Pab)

* as

* (A leftjoin B on (Pab)) leftjoin C on (Pbc)

@@ -1100,9 +1100,10 @@ build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,

bms_is_subset(phv->phrels, sjinfo->syn_lefthand))))

phv->phnullingrels = bms_add_member(phv->phnullingrels,

sjinfo->ojrelid);

- if (bms_overlap(sjinfo->commute_above_r, joinrel->relids))

- phv->phnullingrels = bms_add_members(phv->phnullingrels,

- sjinfo->commute_above_r);

+ phv->phnullingrels =

+ bms_join(phv->phnullingrels,

+ bms_intersect(sjinfo->commute_above_r,

+ relids));

}

joinrel->reltarget->exprs = lappend(joinrel->reltarget->exprs,

@@ -1164,9 +1165,10 @@ build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,

bms_is_member(var->varno, sjinfo->syn_lefthand))))

var->varnullingrels = bms_add_member(var->varnullingrels,

sjinfo->ojrelid);

- if (bms_overlap(sjinfo->commute_above_r, joinrel->relids))

- var->varnullingrels = bms_add_members(var->varnullingrels,

- sjinfo->commute_above_r);

+ var->varnullingrels =

+ bms_join(var->varnullingrels,

+ bms_intersect(sjinfo->commute_above_r,

+ relids));

}

joinrel->reltarget->exprs = lappend(joinrel->reltarget->exprs,

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