I've tried to use Dan Tow's tuning method and created all the right indexes from his diagraming method, but the query still performs quite slow both inside the application and just inside pgadmin III. Can anyone be kind enough to help me tune it so that it performs better in postgres? I don't think it's using the right indexes, or maybe postgres needs special treatment.
I've converted the below query to SQL from a Hibernate query, so the syntax is probably not perfect but it's semantics are exactly the same. I've done so by looking at the source code, but I can't run it to get the exact SQL since I don't have the database on my home machine.
select s.*
from shipment s
inner join carrier_code cc on s.carrier_code_id = cc.id
inner join carrier c on cc.carrier_id = c.id
inner join carrier_to_person ctp on ctp.carrier_id = c.id
inner join person p on p.id = ctp.person_id
inner join shipment_status cs on s.current_status_id = cs.id
inner join release_code rc on cs.release_code_id = rc.id
left join shipment_status ss on ss.shipment_id = s.id
where
p.id = :personId and
s.is_purged = false and
rc.number = '9' and
cs is not null and
cs.date >= current_date - 31
order by cs.date desc
Just assume I have no indexes for the moment because while some of the indexes I made make it work faster, it's still around 250 milliseconds and under heavy load, the query performs very badly (6-7 seconds).
For your information:
shipment contains 40,000 rows
shipment_status contains 80,000 rows
release_code contains 8 rows
person contains 300 rows
carrier contains 60 rows
carrier_code contains 70 rows
The filter ratios are:
rc.number = '9' (0.125)
cs.date >= current_date - 31 (.10)
p.id = ? (0.003)
s.is_purged = false (.98)
I really hope someone can help since I'm pretty much stuck.
Best regards and many thanks,
Ken