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Commit08f1e1f

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Make setrefs.c match by ressortgroupref even for plain Vars.
Previously, we skipped using search_indexed_tlist_for_sortgroupref()if the tlist expression being sought in the child plan node was merelya Var. This is purely an optimization, based on the theory thatsearch_indexed_tlist_for_var() is faster, and one copy of a Var shouldbe as good as another. However, the GROUPING SETS patch broke thelatter assumption: grouping columns containing the "same" Var cansometimes have different outputs, as shown in the test case added here.So do it the hard way whenever a ressortgroupref marking exists.(If this seems like a bottleneck, we could imagine building a tlist indexdata structure for ressortgroupref values, as we do for Vars. But I'lllet that idea go until there's some evidence it's worthwhile.)Back-patch to 9.6. The problem also exists in 9.5 where GROUPING SETScame in, but this patch is insufficient to resolve the problem in 9.5:there is some obscure dependency on the upper-planner-pathificationwork that happened in 9.6. Given that this is such a weird corner case,and no end users have complained about it, it doesn't seem worth the workto develop a fix for 9.5.Patch by me, per a report from Heikki Linnakangas. (This does not fixHeikki's original complaint, just the follow-on one.)Discussion:https://postgr.es/m/aefc657e-edb2-64d5-6df1-a0828f6e9104@iki.fi
1 parent74d2c0d commit08f1e1f

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3 files changed

+43
-4
lines changed

3 files changed

+43
-4
lines changed

‎src/backend/optimizer/plan/setrefs.c

Lines changed: 3 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1744,8 +1744,8 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
17441744
TargetEntry*tle= (TargetEntry*)lfirst(l);
17451745
Node*newexpr;
17461746

1747-
/* If it's anon-Varsort/group item, first try to match by sortref */
1748-
if (tle->ressortgroupref!=0&& !IsA(tle->expr,Var))
1747+
/* If it's a sort/group item, first try to match by sortref */
1748+
if (tle->ressortgroupref!=0)
17491749
{
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newexpr= (Node*)
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search_indexed_tlist_for_sortgroupref(tle->expr,
@@ -2113,7 +2113,6 @@ search_indexed_tlist_for_non_var(Expr *node,
21132113

21142114
/*
21152115
* search_indexed_tlist_for_sortgroupref --- find a sort/group expression
2116-
*(which is assumed not to be just a Var)
21172116
*
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* If a match is found, return a Var constructed to reference the tlist item.
21192118
* If no match, return NULL.
@@ -2644,7 +2643,7 @@ is_converted_whole_row_reference(Node *node)
26442643

26452644
if (IsA(convexpr->arg,Var))
26462645
{
2647-
Var*var=castNode(Var,convexpr->arg);
2646+
Var*var=castNode(Var,convexpr->arg);
26482647

26492648
if (var->varattno==0)
26502649
return true;

‎src/test/regress/expected/groupingsets.out

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -360,6 +360,35 @@ select a, d, grouping(a,b,c)
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2 | 2 | 2
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(4 rows)
362362

363+
-- check that distinct grouping columns are kept separate
364+
-- even if they are equal()
365+
explain (costs off)
366+
select g as alias1, g as alias2
367+
from generate_series(1,3) g
368+
group by alias1, rollup(alias2);
369+
QUERY PLAN
370+
------------------------------------------------
371+
GroupAggregate
372+
Group Key: g, g
373+
Group Key: g
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-> Sort
375+
Sort Key: g
376+
-> Function Scan on generate_series g
377+
(6 rows)
378+
379+
select g as alias1, g as alias2
380+
from generate_series(1,3) g
381+
group by alias1, rollup(alias2);
382+
alias1 | alias2
383+
--------+--------
384+
1 | 1
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1 |
386+
2 | 2
387+
2 |
388+
3 | 3
389+
3 |
390+
(6 rows)
391+
363392
-- simple rescan tests
364393
select a, b, sum(v.x)
365394
from (values (1),(2)) v(x), gstest_data(v.x)

‎src/test/regress/sql/groupingsets.sql

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -141,6 +141,17 @@ select a, d, grouping(a,b,c)
141141
from gstest3
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group by grouping sets ((a,b), (a,c));
143143

144+
-- check that distinct grouping columns are kept separate
145+
-- even if they are equal()
146+
explain (costs off)
147+
select gas alias1, gas alias2
148+
from generate_series(1,3) g
149+
group by alias1, rollup(alias2);
150+
151+
select gas alias1, gas alias2
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from generate_series(1,3) g
153+
group by alias1, rollup(alias2);
154+
144155
-- simple rescan tests
145156

146157
select a, b,sum(v.x)

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