diff options
| 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/statistics/mcv.c | |
| parent | 4a319fce7671ffbe2a730f79529b7a2ef3794d41 (diff) | |
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/statistics/mcv.c')
| -rw-r--r-- | src/backend/statistics/mcv.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/src/backend/statistics/mcv.c b/src/backend/statistics/mcv.c index 6d9a098479d..5410a68bc91 100644 --- a/src/backend/statistics/mcv.c +++ b/src/backend/statistics/mcv.c @@ -1610,7 +1610,6 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses, /* The bitmap may be partially built. */ Assert(clauses != NIL); - Assert(list_length(clauses) >= 1); Assert(mcvlist != NULL); Assert(mcvlist->nitems > 0); Assert(mcvlist->nitems <= STATS_MCVLIST_MAX_ITEMS); |