diff options
| author | David Rowley <drowley@postgresql.org> | 2022-07-13 15:03:47 +1200 |
|---|---|---|
| committer | David Rowley <drowley@postgresql.org> | 2022-07-13 15:03:47 +1200 |
| commit | c23e3e6beb273ae8c0f8e616edb7ed1acb0271c4 (patch) | |
| tree | b0e092c52196ba79555157a75b498b4ea9b8c4d9 /src/backend/optimizer/path/allpaths.c | |
| parent | 50e4c280f0661f3ef837d2c3beb5fcc100202324 (diff) | |
Use list_copy_head() instead of list_truncate(list_copy(...), ...)
Truncating off the end of a freshly copied List is not a very efficient
way of copying the first N elements of a List.
In many of the cases that are updated here, the pattern was only being
used to remove the final element of a List. That's about the best case
for it, but there were many instances where the truncate trimming the List
down much further.
4cc832f94 added list_copy_head(), so let's use it in cases where it's
useful.
Author: David Rowley
Discussion: https://postgr.es/m/1986787.1657666922%40sss.pgh.pa.us
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index e9342097e52..358bb2aed6f 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -2053,9 +2053,8 @@ accumulate_append_subpath(Path *path, List **subpaths, List **special_subpaths) *subpaths = list_concat(*subpaths, list_copy_tail(apath->subpaths, apath->first_partial_path)); - new_special_subpaths = - list_truncate(list_copy(apath->subpaths), - apath->first_partial_path); + new_special_subpaths = list_copy_head(apath->subpaths, + apath->first_partial_path); *special_subpaths = list_concat(*special_subpaths, new_special_subpaths); return; @@ -3086,8 +3085,8 @@ get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel, root->query_pathkeys); else if (npathkeys > 0) useful_pathkeys_list = lappend(useful_pathkeys_list, - list_truncate(list_copy(root->query_pathkeys), - npathkeys)); + list_copy_head(root->query_pathkeys, + npathkeys)); } return useful_pathkeys_list; |