Re: Properly pathify the union planner

On Wed, 7 Feb 2024 at 12:05, Andy Fan <zhihuifan1213@163.com> wrote:
> +static int
> +pathkeys_useful_for_setop(PlannerInfo *root, List *pathkeys)
> +{
> +       int                     n_common_pathkeys;
> +
> +       if (root->setop_pathkeys == NIL)
> +               return 0;                               /* no special setop ordering requested */
> +
> +       if (pathkeys == NIL)
> +               return 0;                               /* unordered path */
> +
> +       (void) pathkeys_count_contained_in(root->setop_pathkeys, pathkeys,
> +                                                                          &n_common_pathkeys);
> +
> +       return n_common_pathkeys;
> +}
>
> The two if-clauses looks unnecessary, it should be handled by
> pathkeys_count_contained_in already. The same issue exists in
> pathkeys_useful_for_ordering as well. Attached patch fix it in master.

I agree.  I'd rather not have those redundant checks in
pathkeys_useful_for_setop(), and I do want those functions to be as
similar as possible.  So I think adjusting it in master is a good
idea.

I've pushed your patch.

David