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Commit28555a5

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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 parent24897e1 commit28555a5

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3 files changed

+24
-5
lines changed

3 files changed

+24
-5
lines changed

‎src/backend/utils/adt/selfuncs.c

Lines changed: 14 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -3587,14 +3587,19 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
35873587
foreach(lc,*varinfos)
35883588
{
35893589
GroupVarInfo*varinfo= (GroupVarInfo*)lfirst(lc);
3590+
AttrNumberattnum;
35903591

35913592
Assert(varinfo->rel==rel);
35923593

3593-
if (IsA(varinfo->var,Var))
3594-
{
3595-
attnums=bms_add_member(attnums,
3596-
((Var*)varinfo->var)->varattno);
3597-
}
3594+
if (!IsA(varinfo->var,Var))
3595+
continue;
3596+
3597+
attnum= ((Var*)varinfo->var)->varattno;
3598+
3599+
if (!AttrNumberIsForUserDefinedAttr(attnum))
3600+
continue;
3601+
3602+
attnums=bms_add_member(attnums,attnum);
35983603
}
35993604

36003605
/* look for the ndistinct statistics matching the most vars */
@@ -3674,6 +3679,10 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
36743679
}
36753680

36763681
attnum= ((Var*)varinfo->var)->varattno;
3682+
3683+
if (!AttrNumberIsForUserDefinedAttr(attnum))
3684+
continue;
3685+
36773686
if (!bms_is_member(attnum,matched))
36783687
newlist=lappend(newlist,varinfo);
36793688
}

‎src/test/regress/expected/stats_ext.out

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -216,6 +216,13 @@ SELECT s.stxkind, d.stxdndistinct
216216
{d,f,m} | {"3, 4": 11, "3, 6": 11, "4, 6": 11, "3, 4, 6": 11}
217217
(1 row)
218218

219+
-- minor improvement, make sure the ctid does not break the matching
220+
SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY ctid, a, b');
221+
estimated | actual
222+
-----------+--------
223+
11 | 1000
224+
(1 row)
225+
219226
-- Hash Aggregate, thanks to estimates improved by the statistic
220227
SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b');
221228
estimated | actual

‎src/test/regress/sql/stats_ext.sql

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -157,6 +157,9 @@ SELECT s.stxkind, d.stxdndistinct
157157
WHEREs.stxrelid='ndistinct'::regclass
158158
ANDd.stxoid=s.oid;
159159

160+
-- minor improvement, make sure the ctid does not break the matching
161+
SELECT*FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY ctid, a, b');
162+
160163
-- Hash Aggregate, thanks to estimates improved by the statistic
161164
SELECT*FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b');
162165

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