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Simplify create_merge_append_path for clarity

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We don't currently support parameterized MergeAppend paths: there's
little use for an ordered path on the inside of a nestloop.  Given
this, we can simplify create_merge_append_path by directly setting
param_info to NULL instead of calling get_appendrel_parampathinfo.  We
can also simplify the Assert for child paths a little bit.

This change won't make any measurable difference in performance; it's
just for clarity's sake.

Author: Richard Guo
Reviewed-by: Alena Rybakina, Paul A Jungwirth
Discussion: https://postgr.es/m/CAMbWs4_n1bgH2nACMuGsXZct3KH6PBFS0tPdQsXdstRfyxTunQ@mail.gmail.com
This commit is contained in:
Richard Guo 2024-07-29 11:33:18 +09:00
parent 2e68077b07
commit f47b33a191
1 changed files with 10 additions and 5 deletions
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15
src/backend/optimizer/util/pathnode.c
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@ -1423,11 +1423,16 @@ create_merge_append_path(PlannerInfo *root,
Cost input_total_cost;
ListCell *l;
/*
* We don't currently support parameterized MergeAppend paths, as
* explained in the comments for generate_orderedappend_paths.
*/
Assert(bms_is_empty(rel->lateral_relids) && bms_is_empty(required_outer));
pathnode->path.pathtype = T_MergeAppend;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = get_appendrel_parampathinfo(rel,
required_outer);
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_workers = 0;
@ -1453,6 +1458,9 @@ create_merge_append_path(PlannerInfo *root,
{
Path *subpath = (Path *) lfirst(l);
/* All child paths should be unparameterized */
Assert(bms_is_empty(PATH_REQ_OUTER(subpath)));
pathnode->path.rows += subpath->rows;
pathnode->path.parallel_safe = pathnode->path.parallel_safe &&
subpath->parallel_safe;
@ -1480,9 +1488,6 @@ create_merge_append_path(PlannerInfo *root,
input_startup_cost += sort_path.startup_cost;
input_total_cost += sort_path.total_cost;
}
/* All child paths must have same parameterization */
Assert(bms_equal(PATH_REQ_OUTER(subpath), required_outer));
}
/*