Robert Haas <robertmh...@gmail.com> writes: > On Mon, Jan 14, 2013 at 12:23 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> The old code definitely had an unreasonably large charge for indexes >> exceeding 1e8 or so tuples. This wouldn't matter that much for simple >> single-table lookup queries, but I could easily see it putting the >> kibosh on uses of an index on the inside of a nestloop.
> The reported behavior was that the planner would prefer to > sequential-scan the table rather than use the index, even if > enable_seqscan=off. I'm not sure what the query looked like, but it > could have been something best implemented as a nested loop w/inner > index-scan. Remember also that "enable_seqscan=off" merely adds 1e10 to the estimated cost of seqscans. For sufficiently large tables this is not exactly a hard disable, just a thumb on the scales. But I don't know what your definition of "extremely large indexes" is. 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