2012/4/16 Tomek Walkuski <tomek.walkuski@xxxxxxxxx>
Hello group!
I have query like this:
SELECT
employments.candidate_id AS candidate_id,
SUM(TS_RANK(employers.search_vector, TO_TSQUERY('simple', 'One:* |
Two:* | Three:* | Four:*'), 2)) AS ts_rank
FROM
employments
INNER JOIN
employers ON employments.employer_id = employers.id
AND
employers.search_vector @@ TO_TSQUERY('simple', 'One:* | Two:* |
Three:* | Four:*')
GROUP BY
candidate_id;
And it results with this:
http://explain.depesz.com/s/jLM
The JOIN between employments and employers is the culprit. I'm unable
to get rid of the seq scan, and setting enable_seqscan to off makes
things even worse.
Is there any way to get rid of this JOIN?
Have you got an index on employments.employer_id? It seems for me that only some employments get out of join, so index would help here. What's the plan with seq_scan off?
P.S. I don't see why all employments are needed. May be I am reading something wrong? For me it's max 2616 employments out of 1606432.
Best regards,
Vitalii Tymchyshyn
