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 merely a Var. This is purely an optimization, based on the theory that search_indexed_tlist_for_var() is faster, and one copy of a Var should be as good as another. However, the GROUPING SETS patch broke the latter assumption: grouping columns containing the "same" Var can sometimes 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 index data structure for ressortgroupref values, as we do for Vars. But I'll let 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 SETS came in, but this patch is insufficient to resolve the problem in 9.5: there is some obscure dependency on the upper-planner-pathification work 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 work to develop a fix for 9.5. Patch by me, per a report from Heikki Linnakangas. (This does not fix Heikki's original complaint, just the follow-on one.) Discussion: https://postgr.es/m/aefc657e-edb2-64d5-6df1-a0828f6e9104@iki.fi
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@ -1744,8 +1744,8 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
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TargetEntry *tle = (TargetEntry *) lfirst(l);
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Node *newexpr;
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/* If it's a non-Var sort/group item, first try to match by sortref */
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if (tle->ressortgroupref != 0 && !IsA(tle->expr, Var))
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/* If it's a sort/group item, first try to match by sortref */
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if (tle->ressortgroupref != 0)
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{
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newexpr = (Node *)
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search_indexed_tlist_for_sortgroupref(tle->expr,
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@ -2113,7 +2113,6 @@ search_indexed_tlist_for_non_var(Expr *node,
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/*
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* search_indexed_tlist_for_sortgroupref --- find a sort/group expression
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* (which is assumed not to be just a Var)
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*
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* If a match is found, return a Var constructed to reference the tlist item.
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* If no match, return NULL.
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@ -2644,7 +2643,7 @@ is_converted_whole_row_reference(Node *node)
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if (IsA(convexpr->arg, Var))
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{
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Var *var = castNode(Var, convexpr->arg);
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Var *var = castNode(Var, convexpr->arg);
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if (var->varattno == 0)
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return true;
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@ -360,6 +360,35 @@ select a, d, grouping(a,b,c)
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2 | 2 | 2
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(4 rows)
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-- check that distinct grouping columns are kept separate
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-- even if they are equal()
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explain (costs off)
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select g as alias1, g as alias2
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from generate_series(1,3) g
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group by alias1, rollup(alias2);
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QUERY PLAN
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------------------------------------------------
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GroupAggregate
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Group Key: g, g
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Group Key: g
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-> Sort
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Sort Key: g
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-> Function Scan on generate_series g
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(6 rows)
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select g as alias1, g as alias2
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from generate_series(1,3) g
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group by alias1, rollup(alias2);
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alias1 | alias2
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--------+--------
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1 | 1
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1 |
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2 | 2
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2 |
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3 | 3
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3 |
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(6 rows)
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-- simple rescan tests
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select a, b, sum(v.x)
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from (values (1),(2)) v(x), gstest_data(v.x)
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@ -141,6 +141,17 @@ select a, d, grouping(a,b,c)
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from gstest3
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group by grouping sets ((a,b), (a,c));
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-- check that distinct grouping columns are kept separate
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-- even if they are equal()
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explain (costs off)
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select g as alias1, g as alias2
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from generate_series(1,3) g
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group by alias1, rollup(alias2);
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select g as alias1, g as alias2
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from generate_series(1,3) g
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group by alias1, rollup(alias2);
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-- simple rescan tests
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select a, b, sum(v.x)
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