attname | attdisbursion | starelid | staattnum | staop | stanullfrac |
stacommonfrac | stacommonval | staloval | stahival
---------+---------------+----------+-----------+-------+-------------+-----
----------+--------------+----------+----------string | 0.00208943 | 1161760 | 1 | 1066 | 0 |
0.0100436 | on | 00 | zzzid | 3.40795e-05 | 1161760 | 2 | 609 | 0 |
0.000170281 | 9807369 | 7647538 | 41122350
(2 rows)
There ya go!
----- Original Message -----
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mitch Vincent <mitch@venux.net>
Cc: <pgsql-sql@postgresql.org>
Sent: Sunday, May 21, 2000 2:28 PM
Subject: Re: [SQL] Full text indexing (and errors!)
> "Mitch Vincent" <mitch@venux.net> writes:
> >> is there an index on applicants' OID column?
>
> > No, there is not an index on the applicant OID column.. Since I'm
getting
> > all the records from the applicants table where the string I search for
is
> > in the resumes_fti table, I didn't think and index like that would help
> > (since I'm qualifying the results based on rows in another table). Am I
> > wrong in thinking that?
>
> If the pattern match is reasonably selective then I'd think that the
> best plan would probably be an indexscan on resumes_fti (using the
> pattern operator to select rows) and then a nestloop join against the
> applicant table using an inner indexscan on OID. In English: look up
> the entries in resumes_fti that match the pattern, and then use the OIDs
> to look up the applicants entries ;-). But it doesn't work without the
> index on OID.
>
> > select count(app_id) from applicants_resumes;
> > 14673
> > select count(id) from resumes_fti;
> > 33462249
>
> Hmm. So the selectivity being estimated for the pattern match is
> 168041/33462249 or about 0.005 ... which is not huge but we'd
> probably like it to be smaller. What do you get from the standard
> statistical query:
>
> select attname,attdisbursion,s.*
> from pg_statistic s, pg_attribute a, pg_class c
> where starelid = c.oid and attrelid = c.oid and staattnum = attnum
> and relname = 'resumes_fti';
>
> regards, tom lane
>
