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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2017-10-26 12:17:40 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2017-10-26 12:17:40 -0400 |
| commit | 6a81ba1d4d26b46636d652a3a56143c159da899c (patch) | |
| tree | b35a8f4777775cd92f7e27f5de84ed662c40e5f5 /src/backend/optimizer/plan/setrefs.c | |
| parent | a9d4625f485abd458f8fcc263f0003235430401e (diff) | |
| download | postgresql-6a81ba1d4d26b46636d652a3a56143c159da899c.tar.gz postgresql-6a81ba1d4d26b46636d652a3a56143c159da899c.zip | |
Make setrefs.c match by ressortgroupref even for plain Vars.
Previously, we skipped using search_indexed_tlist_for_sortgroupref()
if the tlist expression being sought in the child plan node was merely
a Var. This is purely an optimization, based on the theory that
search_indexed_tlist_for_var() is faster, and one copy of a Var should
be as good as another. However, the GROUPING SETS patch broke the
latter assumption: grouping columns containing the "same" Var can
sometimes have different outputs, as shown in the test case added here.
So do it the hard way whenever a ressortgroupref marking exists.
(If this seems like a bottleneck, we could imagine building a tlist index
data structure for ressortgroupref values, as we do for Vars. But I'll
let that idea go until there's some evidence it's worthwhile.)
Back-patch to 9.6. The problem also exists in 9.5 where GROUPING SETS
came in, but this patch is insufficient to resolve the problem in 9.5:
there is some obscure dependency on the upper-planner-pathification
work that happened in 9.6. Given that this is such a weird corner case,
and no end users have complained about it, it doesn't seem worth the work
to develop a fix for 9.5.
Patch by me, per a report from Heikki Linnakangas. (This does not fix
Heikki's original complaint, just the follow-on one.)
Discussion: https://postgr.es/m/aefc657e-edb2-64d5-6df1-a0828f6e9104@iki.fi
Diffstat (limited to 'src/backend/optimizer/plan/setrefs.c')
| -rw-r--r-- | src/backend/optimizer/plan/setrefs.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c index b0c9e944597..90c0bb4a195 100644 --- a/src/backend/optimizer/plan/setrefs.c +++ b/src/backend/optimizer/plan/setrefs.c @@ -1746,8 +1746,8 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset) TargetEntry *tle = (TargetEntry *) lfirst(l); Node *newexpr; - /* If it's a non-Var sort/group item, first try to match by sortref */ - if (tle->ressortgroupref != 0 && !IsA(tle->expr, Var)) + /* If it's a sort/group item, first try to match by sortref */ + if (tle->ressortgroupref != 0) { newexpr = (Node *) search_indexed_tlist_for_sortgroupref(tle->expr, @@ -2108,7 +2108,6 @@ search_indexed_tlist_for_non_var(Expr *node, /* * search_indexed_tlist_for_sortgroupref --- find a sort/group expression - * (which is assumed not to be just a Var) * * If a match is found, return a Var constructed to reference the tlist item. * If no match, return NULL. |