On Fri, May 1, 2015 at 9:13 AM, Bruce Momjian <br...@momjian.us> wrote: > On Fri, May 1, 2015 at 07:57:27AM -0400, Robert Haas wrote: >> On Thu, Apr 30, 2015 at 9:34 PM, Bruce Momjian <br...@momjian.us> wrote: >> > On Wed, Mar 11, 2015 at 02:40:16PM +0000, Andrew Gierth wrote: >> >> An issue that comes up regularly on IRC is that text search queries, >> >> especially on relatively modest size tables or for relatively >> >> non-selective words, often misplan as a seqscan based on the fact that >> >> to_tsvector has procost=1. >> >> >> >> Clearly this cost number is ludicrous. >> >> >> >> Getting the right cost estimate would obviously mean taking the cost of >> >> detoasting into account, but even without doing that, there's a strong >> >> argument that it should be increased to at least the order of 100. >> >> (With the default cpu_operator_cost that would make each to_tsvector >> >> call cost 0.25.) >> >> >> >> (The guy I was just helping on IRC was seeing a slowdown of 100x from a >> >> seqscan in a query that selected about 50 rows from about 500.) >> > >> > Where are we on setting increasing procost for to_tsvector? >> >> We're waiting for you to commit the patch. > > OK, I have to write the patch first, so patch attached, using the cost > of 10. I assume to_tsvector() is the ony one needing changes. The > patch will require a catalog bump too.
Andrew did the research to support a higher value, but even 10 should be an improvement over what we have now. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
