Robert Haas <robertmh...@gmail.com> writes: > On Wed, Feb 29, 2012 at 1:40 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Indeed, and the code already knows that. However, in this example, path >> A is capable of dominating the other three (being strictly less >> parameterized than them), and B and C are each capable of dominating D. >> The problem is just that I'd neglected to consider that rowcount now >> also becomes a figure of merit.
> In theory, yes, but in practice, won't it nearly always be the case > that a less parameterized path generates more rows, and a more > parameterized path generates less rows, so that neither dominates the > other? I think you're just assuming that without any solid evidence. My point is precisely that if the more-parameterized path *fails* to generate fewer rows, we want add_path to notice that and throw it out (or at least be able to throw it out, if there's not another reason to keep it). regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers