diff options
Diffstat (limited to 'src/backend/optimizer/prep/prepjointree.c')
| -rw-r--r-- | src/backend/optimizer/prep/prepjointree.c | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c index 870d84b29d7..2f589b1b99f 100644 --- a/src/backend/optimizer/prep/prepjointree.c +++ b/src/backend/optimizer/prep/prepjointree.c @@ -406,8 +406,8 @@ pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode, * point of the available_rels machinations is to ensure that we only * pull up quals for which that's okay. * - * We don't expect to see any pre-existing JOIN_SEMI or JOIN_ANTI - * nodes here. + * We don't expect to see any pre-existing JOIN_SEMI, JOIN_ANTI, or + * JOIN_RIGHT_ANTI jointypes here. */ switch (j->jointype) { @@ -2640,9 +2640,10 @@ flatten_simple_union_all(PlannerInfo *root) * distribute_qual_to_rels to get rid of such clauses. * * Also, we get rid of JOIN_RIGHT cases by flipping them around to become - * JOIN_LEFT. This saves some code here and in some later planner routines, - * but the main reason to do it is to not need to invent a JOIN_REVERSE_ANTI - * join type. + * JOIN_LEFT. This saves some code here and in some later planner routines; + * the main benefit is to reduce the number of jointypes that can appear in + * SpecialJoinInfo nodes. Note that we can still generate Paths and Plans + * that use JOIN_RIGHT (or JOIN_RIGHT_ANTI) by switching the inputs again. * * To ease recognition of strict qual clauses, we require this routine to be * run after expression preprocessing (i.e., qual canonicalization and JOIN @@ -2896,7 +2897,8 @@ reduce_outer_joins_pass2(Node *jtnode, /* * These could only have been introduced by pull_up_sublinks, * so there's no way that upper quals could refer to their - * righthand sides, and no point in checking. + * righthand sides, and no point in checking. We don't expect + * to see JOIN_RIGHT_ANTI yet. */ break; default: |