Re: Full text indexing (and errors!)

"Mitch Vincent" <mitch(at)venux(dot)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