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Fix confusion in comments about generate_gather_paths

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d2d8a229bc58 introduced a new function generate_useful_gather_paths to
be used as a replacement for generate_gather_paths, but forgot to update
a couple of places that referenced the older function.

This is possibly not 100% complete (ref. create_ordered_paths), but it's
better than not changing anything.

Author: "Hou, Zhijie" <houzj.fnst@cn.fujitsu.com>
Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://postgr.es/m/4ce1d5116fe746a699a6d29858c6a39a@G08CNEXMBPEKD05.g08.fujitsu.local
This commit is contained in:
Alvaro Herrera 2021-02-23 20:04:47 -03:00
parent 8deb6b38dc
commit 5a65eacfdc
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GPG Key ID: 1C20ACB9D5C564AE
2 changed files with 14 additions and 12 deletions
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9
src/backend/optimizer/path/allpaths.c
View File

@ -3019,10 +3019,11 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
join_search_one_level(root, lev); join_search_one_level(root, lev);
/* /*
* Run generate_partitionwise_join_paths() and generate_gather_paths() * Run generate_partitionwise_join_paths() and
* for each just-processed joinrel. We could not do this earlier * generate_useful_gather_paths() for each just-processed joinrel. We
* because both regular and partial paths can get added to a * could not do this earlier because both regular and partial paths
* particular joinrel at multiple times within join_search_one_level. * can get added to a particular joinrel at multiple times within
* join_search_one_level.
* *
* After that, we're done creating paths for the joinrel, so run * After that, we're done creating paths for the joinrel, so run
* set_cheapest(). * set_cheapest().

17
src/backend/optimizer/plan/planner.c
View File

@ -7212,14 +7212,14 @@ create_partial_grouping_paths(PlannerInfo *root,
* Generate Gather and Gather Merge paths for a grouping relation or partial * Generate Gather and Gather Merge paths for a grouping relation or partial
* grouping relation. * grouping relation.
* *
* generate_gather_paths does most of the work, but we also consider a special * generate_useful_gather_paths does most of the work, but we also consider a
* case: we could try sorting the data by the group_pathkeys and then applying * special case: we could try sorting the data by the group_pathkeys and then
* Gather Merge. * applying Gather Merge.
* *
* NB: This function shouldn't be used for anything other than a grouped or * NB: This function shouldn't be used for anything other than a grouped or
* partially grouped relation not only because of the fact that it explicitly * partially grouped relation not only because of the fact that it explicitly
* references group_pathkeys but we pass "true" as the third argument to * references group_pathkeys but we pass "true" as the third argument to
* generate_gather_paths(). * generate_useful_gather_paths().
*/ */
static void static void
gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel) gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
@ -7379,10 +7379,11 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
* variations. So we drop old paths and thereby force the work to be done * variations. So we drop old paths and thereby force the work to be done
* below the Append, except in the case of a non-parallel-safe target. * below the Append, except in the case of a non-parallel-safe target.
* *
* Some care is needed, because we have to allow generate_gather_paths to * Some care is needed, because we have to allow
* see the old partial paths in the next stanza. Hence, zap the main * generate_useful_gather_paths to see the old partial paths in the next
* pathlist here, then allow generate_gather_paths to add path(s) to the * stanza. Hence, zap the main pathlist here, then allow
* main list, and finally zap the partial pathlist. * generate_useful_gather_paths to add path(s) to the main list, and
* finally zap the partial pathlist.
*/ */
if (rel_is_partitioned) if (rel_is_partitioned)
rel->pathlist = NIL; rel->pathlist = NIL;