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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2022-08-17 11:12:35 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2022-08-17 11:12:35 -0400 |
| commit | efd0c16becbf45e3b0215e124fde75fee8fcbce4 (patch) | |
| tree | 4583c8e845ce18ae4a6c6b4c008a4989c514b3cb /src/backend/optimizer/plan/planner.c | |
| parent | 4a319fce7671ffbe2a730f79529b7a2ef3794d41 (diff) | |
| download | postgresql-efd0c16becbf45e3b0215e124fde75fee8fcbce4.tar.gz postgresql-efd0c16becbf45e3b0215e124fde75fee8fcbce4.zip | |
Avoid using list_length() to test for empty list.
The standard way to check for list emptiness is to compare the
List pointer to NIL; our list code goes out of its way to ensure
that that is the only representation of an empty list. (An
acceptable alternative is a plain boolean test for non-null
pointer, but explicit mention of NIL is usually preferable.)
Various places didn't get that memo and expressed the condition
with list_length(), which might not be so bad except that there
were such a variety of ways to check it exactly: equal to zero,
less than or equal to zero, less than one, yadda yadda. In the
name of code readability, let's standardize all those spellings
as "list == NIL" or "list != NIL". (There's probably some
microscopic efficiency gain too, though few of these look to be
at all performance-critical.)
A very small number of cases were left as-is because they seemed
more consistent with other adjacent list_length tests that way.
Peter Smith, with bikeshedding from a number of us
Discussion: https://postgr.es/m/CAHut+PtQYe+ENX5KrONMfugf0q6NHg4hR5dAhqEXEc2eefFeig@mail.gmail.com
Diffstat (limited to 'src/backend/optimizer/plan/planner.c')
| -rw-r--r-- | src/backend/optimizer/plan/planner.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 64632db73cd..e636596b579 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -3097,7 +3097,7 @@ reorder_grouping_sets(List *groupingsets, List *sortclause) GroupingSetData *gs = makeNode(GroupingSetData); while (list_length(sortclause) > list_length(previous) && - list_length(new_elems) > 0) + new_elems != NIL) { SortGroupClause *sc = list_nth(sortclause, list_length(previous)); int ref = sc->tleSortGroupRef; @@ -4120,7 +4120,7 @@ consider_groupingsets_paths(PlannerInfo *root, /* * If we have sorted input but nothing we can do with it, bail. */ - if (list_length(gd->rollups) == 0) + if (gd->rollups == NIL) return; /* @@ -6477,7 +6477,7 @@ add_paths_to_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel, group_clauses, orderAggPathkeys); - Assert(list_length(pathkey_orderings) > 0); + Assert(pathkey_orderings != NIL); /* process all potentially interesting grouping reorderings */ foreach(lc2, pathkey_orderings) @@ -6650,7 +6650,7 @@ add_paths_to_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel, group_clauses, orderAggPathkeys); - Assert(list_length(pathkey_orderings) > 0); + Assert(pathkey_orderings != NIL); /* process all potentially interesting grouping reorderings */ foreach(lc2, pathkey_orderings) @@ -6994,7 +6994,7 @@ create_partial_grouping_paths(PlannerInfo *root, group_clauses, orderAggPathkeys); - Assert(list_length(pathkey_orderings) > 0); + Assert(pathkey_orderings != NIL); /* process all potentially interesting grouping reorderings */ foreach(lc2, pathkey_orderings) @@ -7145,7 +7145,7 @@ create_partial_grouping_paths(PlannerInfo *root, group_clauses, orderAggPathkeys); - Assert(list_length(pathkey_orderings) > 0); + Assert(pathkey_orderings != NIL); /* process all potentially interesting grouping reorderings */ foreach(lc2, pathkey_orderings) |