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| author | Tomas Vondra <tomas.vondra@postgresql.org> | 2021-03-26 22:34:53 +0100 |
|---|---|---|
| committer | Tomas Vondra <tomas.vondra@postgresql.org> | 2021-03-26 22:46:15 +0100 |
| commit | e5eb40eed470ef98e50787ccefe6d32674437be4 (patch) | |
| tree | e4c2fe2780a95bf0ffea93e46e3af4da58f34a7b /src | |
| parent | d544671f1572a0f9138f0e4b3aff38bb683483b2 (diff) | |
Fix ndistinct estimates with system attributes
When estimating the number of groups using extended statistics, the code
was discarding information about system attributes. This led to strange
situation that
SELECT 1 FROM t GROUP BY ctid;
could have produced higher estimate (equal to pg_class.reltuples) than
SELECT 1 FROM t GROUP BY a, b, ctid;
with extended statistics on (a,b). Fixed by retaining information about
the system attribute.
Backpatch all the way to 10, where extended statistics were introduced.
Author: Tomas Vondra
Backpatch-through: 10
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index e128dccb04b..c2f5f948b06 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -3851,11 +3851,11 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel, attnum = ((Var *) varinfo->var)->varattno; - if (!AttrNumberIsForUserDefinedAttr(attnum)) + if (AttrNumberIsForUserDefinedAttr(attnum) && + bms_is_member(attnum, matched)) continue; - if (!bms_is_member(attnum, matched)) - newlist = lappend(newlist, varinfo); + newlist = lappend(newlist, varinfo); } *varinfos = newlist; |