On Fri, May 1, 2015 at 09:39:43AM -0400, Robert Haas wrote: > 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.
Yes, I saw that, but I didn't see him recommend an actual number. Can someone recommend a number now? Tom initially recommended 10, but Andrew's tests suggest something > 100. Tom didn't do any tests so I tend to favor Andrew's suggestion, if he has one. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
