Re: WIP Join Removal

Simon Riggs <simon@2ndQuadrant.com> writes:
> +     if (removable &&
> +         joinrel->cheapest_total_path < keeprel->cheapest_total_path)
> +     {
> +         elog(LOG, "join removed");
> +         joinrel->pathlist = keeprel->pathlist;
> +         joinrel->joininfo = keeprel->baserestrictinfo;
> +     }
> + }

On third thought: if you think that the join paths could possibly win,
then the correct coding here is something like

    foreach(path, keeprel->pathlist)
        add_path(joinrel, ...)

The reason is that it's not an all-or-nothing choice: some of the paths
might offer cheaper startup cost, or present a useful sort order.
So just present them as available alternatives and let add_path sort it
out.

            regards, tom lane