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Fix ndistinct estimates with system attributes

When estimating the number of groups using extended statistics, the codewas discarding information about system attributes. This led to strangesituation 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 aboutthe system attribute.Backpatch all the way to 10, where extended statistics were introduced.Author: Tomas VondraBackpatch-through: 10

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2 files changed

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lines changed

src
- backend/utils/adt
  - selfuncs.c
- test/regress/expected
  - stats_ext.out

2 files changed

-4

lines changed

`‎src/backend/utils/adt/selfuncs.c`

Lines changed: 3 additions & 3 deletions

Original file line number	Diff line number	Diff line change
`@@ -3987,11 +3987,11 @@ estimate_multivariate_ndistinct(PlannerInfo root, RelOptInfo rel,`
`3987`	`3987`
`3988`	`3988`	`attnum= ((Var*)varinfo->var)->varattno;`
`3989`	`3989`
`3990`		`-if (!AttrNumberIsForUserDefinedAttr(attnum))`
	`3990`	`+if (AttrNumberIsForUserDefinedAttr(attnum)&&`
	`3991`	`+bms_is_member(attnum,matched))`
`3991`	`3992`	`continue;`
`3992`	`3993`
`3993`		`-if (!bms_is_member(attnum,matched))`
`3994`		`-newlist=lappend(newlist,varinfo);`
	`3994`	`+newlist=lappend(newlist,varinfo);`
`3995`	`3995`	`}`
`3996`	`3996`
`3997`	`3997`	`*varinfos=newlist;`

`‎src/test/regress/expected/stats_ext.out`

Lines changed: 1 addition & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -260,7 +260,7 @@ SELECT s.stxkind, d.stxdndistinct`
`260`	`260`	`SELECT * FROM check_estimated_rows('SELECT COUNT(*) FROM ndistinct GROUP BY ctid, a, b');`
`261`	`261`	`estimated \| actual`
`262`	`262`	`-----------+--------`
`263`		`- 11 \| 1000`
	`263`	`+1000 \| 1000`
`264`	`264`	`(1 row)`
`265`	`265`
`266`	`266`	`-- Hash Aggregate, thanks to estimates improved by the statistic`

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Commit33e52ad

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2 files changed

2 files changed

`‎src/backend/utils/adt/selfuncs.c`

`‎src/test/regress/expected/stats_ext.out`

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