Re: procost for to_tsvector

On Fri, May  1, 2015 at 07:57:27AM -0400, Robert Haas wrote:
> On Thu, Apr 30, 2015 at 9:34 PM, Bruce Momjian <bruce@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.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + Everyone has their own god. +