Jesper Krogh wrote:
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)
You mean all records of interest, right, not all records in the table?
What indexes do you have in place? What's the schema? Can you post a "\d
tablename" from psql?
# 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)
Without seeing the schema and index definitions ... maybe you'd benefit
from a multiple column index. I'd experiment with an index on
(funcid,priority) first.
--
Craig Ringer
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