Message-ID: <4808DF33.8000008@krogh.cc>
Date: Fri, 18 Apr 2008 19:49:39 +0200
From: Jesper Krogh <jesper@krogh.cc>
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To: pgsql-performance@postgresql.org
Subject: Message queue table.. 
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Hi.

I have this "message queue" table.. currently with 8m+ records. Picking 
the top priority messages seem to take quite long.. it is just a matter 
of searching the index.. (just as explain analyze tells me it does).

Can anyone digest further optimizations out of this output? (All records 
have funcid=4)

# explain analyze SELECT job.jobid, job.funcid, job.arg, job.uniqkey, 
job.insert_time, job.run_after, job.grabbed_until, job.priority, 
job.coalesce FROM workqueue.job  WHERE (job.funcid = 4) AND 
(job.run_after <= 1208442668) AND (job.grabbed_until <= 1208442668) AND 
(job.coalesce = 'Efam') ORDER BY funcid, priority ASC LIMIT 1
;
 
    QUERY PLAN 

--------------------------------------------------------------------------------------------------------------------------------------------------------------
  Limit  (cost=0.00..0.09 rows=1 width=106) (actual 
time=245.273..245.274 rows=1 loops=1)
    ->  Index Scan using workqueue_job_funcid_priority_idx on job 
(cost=0.00..695291.80 rows=8049405 width=106) (actual 
time=245.268..245.268 rows=1 loops=1)
          Index Cond: (funcid = 4)
          Filter: ((run_after <= 1208442668) AND (grabbed_until <= 
1208442668) AND ("coalesce" = 'Efam'::text))
  Total runtime: 245.330 ms
(5 rows)

-- 
Jesper