10000 Disallow SRFs when considering sorts below Gather Merge · postgrespro/postgres_cluster@d016763 · GitHub
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Disallow SRFs when considering sorts below Gather Merge
While we do allow SRFs in ORDER BY, scan/join processing should not consider such cases - such sorts should only happen via final Sort atop a ProjectSet. So make sure we don't try adding such sorts below Gather Merge, just like we do for expressions that are volatile and/or not parallel safe. Backpatch to PostgreSQL 13, where this code was introduced as part of the Incremental Sort patch. Author: James Coleman Reviewed-by: Tomas Vondra Backpatch-through: 13 Discussion: https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs=hC0mSksZC=H5M8LSchj5e5OxpTAg@mail.gmail.com Discussion: https://postgr.es/m/295524.1606246314%40sss.pgh.pa.us
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5 files changed

+26
-5
lines changed
  • util
  • include/optimizer
  • test/regress

    • 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
    @@ -837,6 +837,13 @@ 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

    Lines changed: 0 additions & 5 deletions
    Original file line numberDiff line numberDiff line change
    @@ -21,11 +21,6 @@
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    #include "optimizer/tlist.h"
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    24-
    /* Test if an expression node represents a SRF call. Beware multiple eval! */
    25-
    #define IS_SRF_CALL(node) \
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    ((IsA(node, FuncExpr) && ((FuncExpr *) (node))->funcretset) || \
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    (IsA(node, OpExpr) && ((OpExpr *) (node))->opretset))
    28-
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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

    Lines changed: 5 additions & 0 deletions
    Original file line numberDiff line numberDiff line change
    @@ -24,6 +24,11 @@
    2424

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    #include "nodes/parsenodes.h"
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    27+
    /* Test if an expression node represents a SRF call. Beware multiple eval! */
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    #define IS_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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    2732
    /*
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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

    Lines changed: 12 additions & 0 deletions
    Original file line numberDiff line numberDiff line change
    @@ -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

    Lines changed: 2 additions & 0 deletions
    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) select sub.unique1, stringu1 || random()::text
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    from tenk1, lateral (select tenk1.unique1 from generate_series(1, 1000)) as sub
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    order by 1, 2;
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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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