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Hi,

I'm having some trouble getting this query down for large users.
Basically, we deal with competition entries. For this customer (a.k.a.
site) we've got ~1,000,000 entries from ~100,000 contestants.

SELECT contestants.*, sum(entries.worth) as db_entries, count(entries.id)
as db_actions FROM "contestants" INNER JOIN "entries" ON
"entries"."contestant_id" = "contestants"."id" WHERE
"entries"."campaign_id" IN (SELECT id FROM "campaigns" WHERE
"campaigns"."site_id" = $1) AND (entries.status != 'Invalid') GROUP BY
contestants.id ORDER BY db_actions desc LIMIT 20 OFFSET 0

Here's the explain:

QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=3783168.28..3783168.33 rows=20 width=103)
-> Sort (cost=3783168.28..3792902.85 rows=3893825 width=103)
Sort Key: (count(entries.id))
-> GroupAggregate (cost=3004896.86..3679555.00 rows=3893825
width=103)
-> Merge Join (cost=3004896.86..3611413.06 rows=3893825
width=103)
Merge Cond: (contestants.id = entries.contestant_id)
-> Index Scan using contestants_pkey on contestants
(cost=0.43..534782.85 rows=7490021 width=95)
-> Sort (cost=3004710.57..3014464.64 rows=3901628
width=12)
Sort Key: entries.contestant_id
-> Nested Loop (cost=19.88..2577567.27
rows=3901628 width=12)
-> Bitmap Heap Scan on campaigns
(cost=19.32..1332.62 rows=374 width=4)
Recheck Cond: (site_id = 152)
-> Bitmap Index Scan on
index_campaigns_on_site_id (cost=0.00..19.22 rows=374 width=0)
Index Cond: (site_id = 152)
-> Index Scan using
index_entries_on_campaign_id on entries (cost=0.57..6784.01 rows=10432
width=16)
Index Cond: (campaign_id =
campaigns.id)
Filter: ((status)::text <>
'Invalid'::text)

Any thoughts on tweaks I could apply to speed this up?

Thanks,

John