Re: Incremental sort for access method with ordered scan support (amcanorderbyop) - Mailing list pgsql-hackers

On Tue, 18 Apr 2023 at 19:29, Miroslav Bendik <miroslav.bendik@gmail.com> wrote:
> here is an updated patch with proposed changes.

Here's a quick review:

1. I don't think this is required. match_pathkeys_to_index() sets
these to NIL and they're set accordingly by the other code paths.

- List    *orderbyclauses;
- List    *orderbyclausecols;
+ List    *orderbyclauses = NIL;
+ List    *orderbyclausecols = NIL;

2. You can use list_copy_head(root->query_pathkeys,
list_length(orderbyclauses)); instead of:

+ useful_pathkeys = list_truncate(list_copy(root->query_pathkeys),
+     list_length(orderbyclauses));

3. The following 2 changes don't seem to be needed:

@@ -3104,11 +3100,11 @@ match_pathkeys_to_index(IndexOptInfo *index,
List *pathkeys,
  /* Pathkey must request default sort order for the target opfamily */
  if (pathkey->pk_strategy != BTLessStrategyNumber ||
      pathkey->pk_nulls_first)
-     return;
+     break;

  /* If eclass is volatile, no hope of using an indexscan */
  if (pathkey->pk_eclass->ec_has_volatile)
-     return;
+     break;

There's no code after the loop you're breaking out of, so it seems to
me that return is the same as break and there's no reason to change
it.

David