Re: SQL Query Performance - what gives?

Karl Denninger <karl(at)denninger(dot)net> wrote:
> -> Index Scan using forum_name on forum
> (cost=0.00..250.63 rows=1 width=271) (actual time=0.013..0.408
> rows=63 loops=1)
> Filter: (((contrib IS NULL) OR (contrib = '
> '::text) OR (contrib ~~ '%b%'::text)) AND ((permission & 127) =
> permission))

The biggest issue, as far as I can see, is that it thinks that the
selection criteria on forum will limit to one row, while it really
matches 63 rows.

You might be able to coerce it into a faster plan with something like
this (untested):

select *
from (select * from post
where invisible <> 1
and to_tsvector('english', message)
@@ to_tsquery('violence')
) p,
forum
where forum.name = p.forum
and (permission & '127') = permission
and (contrib is null or contrib = ' ' or contrib like '%b%')
order by modified desc
limit 100
;

-Kevin