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Skip system attributes when applying mvdistinct stats

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When estimating number of distinct groups, we failed to ignore system
attributes when matching the group expressions to mvdistinct stats,
causing failures like

  ERROR: negative bitmapset member not allowed

Fix that by simply skipping anything that is not a regular attribute.
Backpatch to PostgreSQL 10, where the extended stats were introduced.

Bug: #16111
Reported-by: Tuomas Leikola
Author: Tomas Vondra
Backpatch-through: 10
Discussion: https://postgr.es/m/16111-687799584c3a7e73@postgresql.org
This commit is contained in:
Tomas Vondra 2019-11-16 01:17:15 +01:00
parent 76cbfcdf3a
commit d482f7f867
3 changed files with 24 additions and 5 deletions
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19
src/backend/utils/adt/selfuncs.c
View File

@ -3582,14 +3582,19 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
foreach(lc, *varinfos) foreach(lc, *varinfos)
{ {
GroupVarInfo *varinfo = (GroupVarInfo *) lfirst(lc); GroupVarInfo *varinfo = (GroupVarInfo *) lfirst(lc);
AttrNumber attnum;
Assert(varinfo->rel == rel); Assert(varinfo->rel == rel);
if (IsA(varinfo->var, Var)) if (!IsA(varinfo->var, Var))
{ continue;
attnums = bms_add_member(attnums,
((Var *) varinfo->var)->varattno); attnum = ((Var *) varinfo->var)->varattno;
}
if (!AttrNumberIsForUserDefinedAttr(attnum))
continue;
attnums = bms_add_member(attnums, attnum);
} }
/* look for the ndistinct statistics matching the most vars */ /* look for the ndistinct statistics matching the most vars */
@ -3669,6 +3674,10 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
} }
attnum = ((Var *) varinfo->var)->varattno; attnum = ((Var *) varinfo->var)->varattno;
if (!AttrNumberIsForUserDefinedAttr(attnum))
continue;
if (!bms_is_member(attnum, matched)) if (!bms_is_member(attnum, matched))
newlist = lappend(newlist, varinfo); newlist = lappend(newlist, varinfo);
} }

7
src/test/regress/expected/stats_ext.out
View File

@ -233,6 +233,13 @@ SELECT s.stxkind, d.stxdndistinct
{d,f,m} | {"3, 4": 11, "3, 6": 11, "4, 6": 11, "3, 4, 6": 11} {d,f,m} | {"3, 4": 11, "3, 6": 11, "4, 6": 11, "3, 4, 6": 11}
(1 row) (1 row)
-- minor improvement, make sure the ctid does not break the matching
SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY ctid, a, b');
estimated | actual
-----------+--------
11 | 1000
(1 row)
-- Hash Aggregate, thanks to estimates improved by the statistic -- Hash Aggregate, thanks to estimates improved by the statistic
SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b'); SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b');
estimated | actual estimated | actual

3
src/test/regress/sql/stats_ext.sql
View File

@ -167,6 +167,9 @@ SELECT s.stxkind, d.stxdndistinct
WHERE s.stxrelid = 'ndistinct'::regclass WHERE s.stxrelid = 'ndistinct'::regclass
AND d.stxoid = s.oid; AND d.stxoid = s.oid;
-- minor improvement, make sure the ctid does not break the matching
SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY ctid, a, b');
-- Hash Aggregate, thanks to estimates improved by the statistic -- Hash Aggregate, thanks to estimates improved by the statistic
SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b'); SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY a, b');