On Mon, Jan 5, 2009 at 11:40 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > "Robert Haas" <robertmhaas@xxxxxxxxx> writes: >> While looking at a complex query that is being poorly planned by >> PostgreSQL 8.2.9, I discovered that any non-trivial CASE...WHEN >> expression seems to produce a selectivity estimate of 0.005. > > If you have an idea for a non-silly estimate, feel free to enlighten > us... Well, presumably CASE WHEN <expr1> THEN <constant1> WHEN <expr2> THEN <constant2> WHEN <expr3> THEN <constant3> ... END = <constantn> could be simplified to <exprn>. But that's not going to happen in time to do me any good on this query, if it ever happens (and might not be sufficient anyway since the selectivity estimates of <expr1> may not be very good either), so I was more looking for suggestions on coping with the situation, since I'm sure that I'm not the first person to have this type of problem. ...Robert -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
