diff options
Diffstat (limited to 'src/backend/optimizer/path/joinrels.c')
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 33 |
1 files changed, 30 insertions, 3 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index 6ddf8461257..50fc0c500d0 100644 --- a/src/backend/optimizer/path/joinrels.c +++ b/src/backend/optimizer/path/joinrels.c @@ -33,7 +33,6 @@ static void make_rels_by_clauseless_joins(PlannerInfo *root, ListCell *other_rels); static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel); static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel); -static bool is_dummy_rel(RelOptInfo *rel); static bool restriction_is_constant_false(List *restrictlist, RelOptInfo *joinrel, bool only_pushed_down); @@ -1192,10 +1191,38 @@ have_dangerous_phv(PlannerInfo *root, /* * is_dummy_rel --- has relation been proven empty? */ -static bool +bool is_dummy_rel(RelOptInfo *rel) { - return IS_DUMMY_REL(rel); + Path *path; + + /* + * A rel that is known dummy will have just one path that is a childless + * Append. (Even if somehow it has more paths, a childless Append will + * have cost zero and hence should be at the front of the pathlist.) + */ + if (rel->pathlist == NIL) + return false; + path = (Path *) linitial(rel->pathlist); + + /* + * Initially, a dummy path will just be a childless Append. But in later + * planning stages we might stick a ProjectSetPath and/or ProjectionPath + * on top, since Append can't project. Rather than make assumptions about + * which combinations can occur, just descend through whatever we find. + */ + for (;;) + { + if (IsA(path, ProjectionPath)) + path = ((ProjectionPath *) path)->subpath; + else if (IsA(path, ProjectSetPath)) + path = ((ProjectSetPath *) path)->subpath; + else + break; + } + if (IS_DUMMY_APPEND(path)) + return true; + return false; } /* |