diff options
Diffstat (limited to 'src/backend/optimizer/util/relnode.c')
| -rw-r--r-- | src/backend/optimizer/util/relnode.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c index 996b7fe5136..8cc7bd771b3 100644 --- a/src/backend/optimizer/util/relnode.c +++ b/src/backend/optimizer/util/relnode.c @@ -500,6 +500,47 @@ build_join_rel(PlannerInfo *root, } /* + * min_join_parameterization + * + * Determine the minimum possible parameterization of a joinrel, that is, the + * set of other rels it contains LATERAL references to. We save this value in + * the join's RelOptInfo. This function is split out of build_join_rel() + * because join_is_legal() needs the value to check a prospective join. + */ +Relids +min_join_parameterization(PlannerInfo *root, Relids joinrelids) +{ + Relids result; + ListCell *lc; + + /* Easy if there are no lateral references */ + if (root->lateral_info_list == NIL) + return NULL; + + /* + * Scan lateral_info_list to find all the lateral references occurring in + * or below this join. + */ + result = NULL; + foreach(lc, root->lateral_info_list) + { + LateralJoinInfo *ljinfo = (LateralJoinInfo *) lfirst(lc); + + if (bms_is_subset(ljinfo->lateral_rhs, joinrelids)) + result = bms_add_members(result, ljinfo->lateral_lhs); + } + + /* Remove any rels that are already included in the join */ + result = bms_del_members(result, joinrelids); + + /* Maintain invariant that result is exactly NULL if empty */ + if (bms_is_empty(result)) + result = NULL; + + return result; +} + +/* * build_joinrel_tlist * Builds a join relation's target list from an input relation. * (This is invoked twice to handle the two input relations.) |