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Commitfac1b47

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Disallow SRFs when considering sorts below Gather Merge
While we do allow SRFs in ORDER BY, scan/join processing should notconsider such cases - such sorts should only happen via final Sort atopa ProjectSet. So make sure we don't try adding such sorts below GatherMerge, just like we do for expressions that are volatile and/or notparallel safe.Backpatch to PostgreSQL 13, where this code was introduced as part ofthe Incremental Sort patch.Author: James ColemanReviewed-by: Tomas VondraBackpatch-through: 13Discussion:https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs=hC0mSksZC=H5M8LSchj5e5OxpTAg@mail.gmail.comDiscussion:https://postgr.es/m/295524.1606246314%40sss.pgh.pa.us
1 parentff5d561 commitfac1b47

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5 files changed

+26
-5
lines changed

5 files changed

+26
-5
lines changed

‎src/backend/optimizer/path/equivclass.c

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Original file line numberDiff line numberDiff line change
@@ -840,6 +840,13 @@ find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec,
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if (require_parallel_safe&& !is_parallel_safe(root, (Node*)em_expr))
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continue;
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/*
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* Disallow SRFs so that all of them can be evaluated at the correct
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* time as determined by make_sort_input_target.
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*/
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if (IS_SRF_CALL((Node*)em_expr))
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continue;
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/*
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* As long as the expression isn't volatile then
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* prepare_sort_from_pathkeys is able to generate a new target entry,

‎src/backend/optimizer/util/tlist.c

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@@ -21,11 +21,6 @@
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#include"optimizer/tlist.h"
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/* Test if an expression node represents a SRF call. Beware multiple eval! */
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#defineIS_SRF_CALL(node) \
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((IsA(node, FuncExpr) && ((FuncExpr *) (node))->funcretset) || \
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(IsA(node, OpExpr) && ((OpExpr *) (node))->opretset))
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/*
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* Data structures for split_pathtarget_at_srfs(). To preserve the identity
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* of sortgroupref items even if they are textually equal(), what we track is

‎src/include/optimizer/optimizer.h

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@@ -24,6 +24,11 @@
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#include"nodes/parsenodes.h"
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/* Test if an expression node represents a SRF call. Beware multiple eval! */
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#defineIS_SRF_CALL(node) \
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((IsA(node, FuncExpr) && ((FuncExpr *) (node))->funcretset) || \
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(IsA(node, OpExpr) && ((OpExpr *) (node))->opretset))
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/*
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* We don't want to include nodes/pathnodes.h here, because non-planner
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* code should generally treat PlannerInfo as an opaque typedef.

‎src/test/regress/expected/incremental_sort.out

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@@ -1620,3 +1620,15 @@ order by 1, 2;
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-> Function Scan on generate_series
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(7 rows)
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-- Disallow pushing down sort when pathkey is an SRF.
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explain (costs off) select unique1 from tenk1 order by unnest('{1,2}'::int[]);
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QUERY PLAN
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-------------------------------------------------------------------------
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Sort
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Sort Key: (unnest('{1,2}'::integer[]))
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-> Gather
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Workers Planned: 2
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-> ProjectSet
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-> Parallel Index Only Scan using tenk1_unique1 on tenk1
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(6 rows)
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‎src/test/regress/sql/incremental_sort.sql

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Original file line numberDiff line numberDiff line change
@@ -267,3 +267,5 @@ from tenk1, lateral (select tenk1.unique1 from generate_series(1, 1000)) as sub;
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explain (costs off)selectsub.unique1, stringu1|| random()::text
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from tenk1, lateral (selecttenk1.unique1from generate_series(1,1000))as sub
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order by1,2;
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-- Disallow pushing down sort when pathkey is an SRF.
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explain (costs off)select unique1from tenk1order by unnest('{1,2}'::int[]);

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