Tom Lane wrote: > John A Meinel <[EMAIL PROTECTED]> writes: > >>What I don't understand is that the planner is actually estimating that >>joining against the new table is going to *increase* the number of >>returned rows. > > > It evidently thinks that incidentid in the k_r table is pretty > nonunique. We really need to look at the statistics data to > see what's going on. > > regards, tom lane >
Okay, sure. What about doing this, then:
EXPLAIN ANALYZE
SELECT recordtext FROM eventactivity
JOIN (SELECT DISTINCT incidentid FROM k_r JOIN k_b USING (incidentid)
WHERE k_r.id = ?? AND k_b.id = ??)
USING (incidentid)
;
Since I assume that eventactivity is the only table with "recordtext",
and that you don't get any columns from k_r and k_b, meaning it would be
pointless to get duplicate incidentids.
I may be misunderstanding what the query is trying to do, but depending
on what is in k_r and k_b, is it possible to use a UNIQUE INDEX rather
than just an index on incidentid?
There is also the possibility of
EXPLAIN ANALYZE
SELECT recordtext FROM eventactivtity
JOIN (SELECT incidentid FROM k_r WHERE k_r.id = ??
UNION SELECT incidentid FROM k_b WHERE k_b.id = ??)
USING (incidentid)
;
But both of these would mean that you don't actually want columns from
k_r or k_b, just a unique list of incident ids.
But first, I agree, we should make sure the pg_stats values are reasonable.
John
=:->
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