diff options
Diffstat (limited to 'src/backend/optimizer/util/relnode.c')
| -rw-r--r-- | src/backend/optimizer/util/relnode.c | 43 |
1 files changed, 24 insertions, 19 deletions
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c index ad84cc43e11..29da78b62ef 100644 --- a/src/backend/optimizer/util/relnode.c +++ b/src/backend/optimizer/util/relnode.c @@ -1043,23 +1043,23 @@ min_join_parameterization(PlannerInfo *root, * two joins had been done in syntactic order; else they won't match Vars * appearing higher in the query tree. We need to do two things: * - * First, sjinfo->commute_above_r is added to the nulling bitmaps of RHS Vars. - * This takes care of the case where we implement + * First, we add the outer join's relid to the nulling bitmap only if the Var + * or PHV actually comes from within the syntactically nullable side(s) of the + * outer join. This takes care of the possibility that we have transformed + * (A leftjoin B on (Pab)) leftjoin C on (Pbc) + * to + * 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 * A leftjoin (B leftjoin C on (Pbc)) on (Pab) * as * (A leftjoin B on (Pab)) leftjoin C on (Pbc) * The C columns emitted by the B/C join need to be shown as nulled by both - * the B/C and A/B joins, even though they've not traversed the A/B join. - * (If the joins haven't been commuted, we are adding the nullingrel bits - * prematurely; but that's okay because the C columns can't be referenced - * between here and the upper join.) - * - * Second, if a RHS Var has any of the relids in sjinfo->commute_above_l - * already set in its nulling bitmap, then we *don't* add sjinfo->ojrelid - * to its nulling bitmap (but we do still add commute_above_r). This takes - * care of the reverse transformation: if the original syntax was - * (A leftjoin B on (Pab)) leftjoin C on (Pbc) - * then the now-upper A/B join must not mark C columns as nulled by itself. + * the B/C and A/B joins, even though they've not physically traversed the + * A/B join. */ static void build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel, @@ -1095,10 +1095,12 @@ build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel, phv = copyObject(phv); /* See comments above to understand this logic */ if (sjinfo->ojrelid != 0 && - !bms_overlap(phv->phnullingrels, sjinfo->commute_above_l)) + (bms_is_subset(phv->phrels, sjinfo->syn_righthand) || + (sjinfo->jointype == JOIN_FULL && + bms_is_subset(phv->phrels, sjinfo->syn_lefthand)))) phv->phnullingrels = bms_add_member(phv->phnullingrels, sjinfo->ojrelid); - if (sjinfo->commute_above_r) + if (bms_overlap(sjinfo->commute_above_r, joinrel->relids)) phv->phnullingrels = bms_add_members(phv->phnullingrels, sjinfo->commute_above_r); } @@ -1149,17 +1151,20 @@ build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel, /* * Add the Var to the output. If this join potentially nulls this * input, we have to update the Var's varnullingrels, which means - * making a copy. + * making a copy. But note that we don't ever add nullingrel bits to + * row identity Vars (cf. comments in setrefs.c). */ - if (can_null) + if (can_null && var->varno != ROWID_VAR) { var = copyObject(var); /* See comments above to understand this logic */ if (sjinfo->ojrelid != 0 && - !bms_overlap(var->varnullingrels, sjinfo->commute_above_l)) + (bms_is_member(var->varno, sjinfo->syn_righthand) || + (sjinfo->jointype == JOIN_FULL && + bms_is_member(var->varno, sjinfo->syn_lefthand)))) var->varnullingrels = bms_add_member(var->varnullingrels, sjinfo->ojrelid); - if (sjinfo->commute_above_r) + if (bms_overlap(sjinfo->commute_above_r, joinrel->relids)) var->varnullingrels = bms_add_members(var->varnullingrels, sjinfo->commute_above_r); } |