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Commit0b0f281

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Skip system attributes when applying mvdistinct stats
When estimating number of distinct groups, we failed to ignore systemattributes when matching the group expressions to mvdistinct stats,causing failures like ERROR: negative bitmapset member not allowedFix that by simply skipping anything that is not a regular attribute.Backpatch to PostgreSQL 10, where the extended stats were introduced.Bug: #16111Reported-by: Tuomas LeikolaAuthor: Tomas VondraBackpatch-through: 10Discussion:https://postgr.es/m/16111-687799584c3a7e73@postgresql.org
1 parent4be69e2 commit0b0f281

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3 files changed

+30
-5
lines changed

3 files changed

+30
-5
lines changed

‎src/backend/utils/adt/selfuncs.c

Lines changed: 14 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -3757,14 +3757,19 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
37573757
foreach(lc,*varinfos)
37583758
{
37593759
GroupVarInfo*varinfo= (GroupVarInfo*)lfirst(lc);
3760+
AttrNumberattnum;
37603761

37613762
Assert(varinfo->rel==rel);
37623763

3763-
if (IsA(varinfo->var,Var))
3764-
{
3765-
attnums=bms_add_member(attnums,
3766-
((Var*)varinfo->var)->varattno);
3767-
}
3764+
if (!IsA(varinfo->var,Var))
3765+
continue;
3766+
3767+
attnum= ((Var*)varinfo->var)->varattno;
3768+
3769+
if (!AttrNumberIsForUserDefinedAttr(attnum))
3770+
continue;
3771+
3772+
attnums=bms_add_member(attnums,attnum);
37683773
}
37693774

37703775
/* look for the ndistinct statistics matching the most vars */
@@ -3844,6 +3849,10 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
38443849
}
38453850

38463851
attnum= ((Var*)varinfo->var)->varattno;
3852+
3853+
if (!AttrNumberIsForUserDefinedAttr(attnum))
3854+
continue;
3855+
38473856
if (!bms_is_member(attnum,matched))
38483857
newlist=lappend(newlist,varinfo);
38493858
}

‎src/test/regress/expected/stats_ext.out

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -217,6 +217,18 @@ SELECT stxkind, stxndistinct
217217
{d,f} | {"3, 4": 301, "3, 6": 301, "4, 6": 301, "3, 4, 6": 301}
218218
(1 row)
219219

220+
-- minor improvement, make sure the ctid does not break the matching
221+
EXPLAIN (COSTS off)
222+
SELECT COUNT(*) FROM ndistinct GROUP BY ctid, a, b;
223+
QUERY PLAN
224+
-----------------------------------
225+
GroupAggregate
226+
Group Key: ctid, a, b
227+
-> Sort
228+
Sort Key: ctid, a, b
229+
-> Seq Scan on ndistinct
230+
(5 rows)
231+
220232
-- Hash Aggregate, thanks to estimates improved by the statistic
221233
EXPLAIN (COSTS off)
222234
SELECT COUNT(*) FROM ndistinct GROUP BY a, b;

‎src/test/regress/sql/stats_ext.sql

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -144,6 +144,10 @@ ANALYZE ndistinct;
144144
SELECT stxkind, stxndistinct
145145
FROM pg_statistic_extWHERE stxrelid='ndistinct'::regclass;
146146

147+
-- minor improvement, make sure the ctid does not break the matching
148+
EXPLAIN (COSTS off)
149+
SELECTCOUNT(*)FROM ndistinctGROUP BY ctid, a, b;
150+
147151
-- Hash Aggregate, thanks to estimates improved by the statistic
148152
EXPLAIN (COSTS off)
149153
SELECTCOUNT(*)FROM ndistinctGROUP BY a, b;

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