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Track the number of presorted outer pathkeys in MergePath

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When creating an explicit Sort node for the outer path of a mergejoin,
we need to determine the number of presorted keys of the outer path to
decide whether explicit incremental sort can be applied.  Currently,
this is done by repeatedly calling pathkeys_count_contained_in.

This patch caches the number of presorted outer pathkeys in MergePath,
allowing us to save several calls to pathkeys_count_contained_in.  It
can be considered a complement to the changes in commit 828e94c9d.

Reported-by: David Rowley <dgrowleyml@gmail.com>
Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Tender Wang <tndrwang@gmail.com>
Discussion: https://postgr.es/m/CAApHDvqvBireB_w6x8BN5txdvBEHxVgZBt=rUnpf5ww5P_E_ww@mail.gmail.com
This commit is contained in:
Richard Guo
2025-05-08 18:21:32 +09:00
parent 773db22269
commit c06e909c26
8 changed files with 104 additions and 66 deletions
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8
src/include/nodes/pathnodes.h
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@@ -2253,6 +2253,12 @@ typedef struct NestPath
* mergejoin. If it is not NIL then it is a PathKeys list describing
* the ordering that must be created by an explicit Sort node.
*
* outer_presorted_keys is the number of presorted keys of the outer
* path that match outersortkeys. It is used to determine whether
* explicit incremental sort can be applied when outersortkeys is not
* NIL. We do not track the number of presorted keys of the inner
* path, as incremental sort currently does not support mark/restore.
*
* skip_mark_restore is true if the executor need not do mark/restore calls.
* Mark/restore overhead is usually required, but can be skipped if we know
* that the executor need find only one match per outer tuple, and that the
@@ -2270,6 +2276,8 @@ typedef struct MergePath
List *path_mergeclauses; /* join clauses to be used for merge */
List *outersortkeys; /* keys for explicit sort, if any */
List *innersortkeys; /* keys for explicit sort, if any */
int outer_presorted_keys; /* number of presorted keys of the
* outer path */
bool skip_mark_restore; /* can executor skip mark/restore? */
bool materialize_inner; /* add Materialize to inner? */
} MergePath;