Here is my select right after initdb:
postgres=# select name,setting from pg_settings where name like '%_cost';
name | setting
----------------------+-------
-- cpu_index_tuple_cost | 0.005
cpu_operator_cost | 0.0025
cpu_tuple_cost | 0.01
parallel_setup_cost | 1000
parallel_tuple_cost | 0.1
random_page_cost | 4
seq_page_cost | 1
Can you generate plan with random_page_cost = 4?
--
Alex Ignatov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
From: Dmitry Shalashov [mailto:skaurus@xxxxxxxxx]
Sent: Wednesday, November 22, 2017 5:29 PM
To: Alex Ignatov <a.ignatov@xxxxxxxxxxxxxx>
Cc: pgsql-performance@postgresql.org
Subject: Re: Query became very slow after 9.6 -> 10 upgrade
Sure, here it goes:
name | setting
----------------------+-------
-- cpu_index_tuple_cost | 0.005
cpu_operator_cost | 0.0025
cpu_tuple_cost | 0.01
parallel_setup_cost | 1000
parallel_tuple_cost | 0.1
random_page_cost | 1
seq_page_cost | 1
Dmitry Shalashov, relap.io & surfingb
ird.ru
2017-11-22 17:24 GMT+03:00 Alex Ignatov <a.ignatov@xxxxxxxxxxxxxx>:
Hello!
What about :
select name,setting from pg_settings where name like '%_cost';
--
Alex Ignatov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
From: Dmitry Shalashov [mailto:skaurus@xxxxxxxxx]
Sent: Wednesday, November 22, 2017 5:14 PM
To: pgsql-performance@postgresql.org
Subject: Query became very slow after 9.6 -> 10 upgrade
Hi!
I've seen few letters like this on mailing list and for some reason thought that probably it won't happen to us, but here I am lol.
It's "nestloop hits again" situation.
I'll try to provide plan from 9.6 later, but right now I have only plan from 10.1.
It was running under 3 seconds (it's our default timeout) and now it runs for 12 minutes.
\d adroom: https://pastebin.com/
vBrPGtxT (3800 rows)\d adroom_stat: https://pastebin.
com/CkBArCC9 (47mln rows, 1.5mln satisfy condition on day column)\d domains: https://pastebin.com/
65hk7YCm (73000 rows)
All three tables are analyzed.
EXPLAIN ANALYZE: https://pastebin.com/
PenHEgf0 EXPLAIN ANALYZE with nestloop off: https://pastebin.com/
zX35CPCV (0.8s)
Regarding server parameters - it's a mighty beast with 2x E5-2630 v3, 192Gb of RAM and two very, very fast NVME server class SSD's in RAID1.
What can I do with it?
Also maybe this will be useful:
1st query, runs under 1ms
select title, id, groups->0->>'provider' provider, domain_ids from adroom where groups->0->>'provider' ~ '^target_mail_ru' and not is_paused and current_timestamp between start_ts and stop_ts
2nd query that uses 1st one, runs under 3 ms
select distinct unnest(domain_ids) FROM (select title, id, groups->0->>'provider' provider, domain_ids from adroom where groups->0->>'provider' ~ '^target_mail_ru' and not is_paused and current_timestamp between start_ts and stop_ts) t1
3rd query which returns 1.5mln rows, runs in about 0.6s
SELECT adroom_id, domain_id, shows, clicks FROM adroom_stat WHERE day between date_trunc('day', current_timestamp - interval '1 week') and date_trunc('day', current_timestamp)
BUT if I'll add to 3rd query one additional condition, which is basically 2nd query, it will ran same 12 minutes:
SELECT adroom_id, domain_id, shows, clicks FROM adroom_stat WHERE day between date_trunc('day', current_timestamp - interval '1 week') and date_trunc('day', current_timestamp) AND domain_id IN (select distinct unnest(domain_ids) FROM (select title, id, groups->0->>'provider' provider, domain_ids from adroom where groups->0->>'provider' ~ '^target_mail_ru' and not is_paused and current_timestamp between start_ts and stop_ts) t1)
Plan of last query:
Nested Loop (cost=88.63..25617.31 rows=491 width=16) (actual time=3.512..733248.271 rows=1442797 loops=1)
-> HashAggregate (cost=88.06..88.07 rows=1 width=4) (actual time=3.380..13.561 rows=3043 loops=1)
Group Key: (unnest(adroom.domain_ids))
-> HashAggregate (cost=88.03..88.04 rows=1 width=4) (actual time=2.199..2.607 rows=3043 loops=1)
Group Key: unnest(adroom.domain_ids)
-> ProjectSet (cost=0.28..87.78 rows=100 width=4) (actual time=0.701..1.339 rows=3173 loops=1)
-> Index Scan using adroom_active_idx on adroom (cost=0.28..87.27 rows=1 width=167) (actual time=0.688..1.040 rows=4 loops=1)
Index Cond: ((CURRENT_TIMESTAMP >= start_ts) AND (CURRENT_TIMESTAMP <= stop_ts))
Filter: (((groups -> 0) ->> 'provider'::text) ~ '^target_mail_ru'::text)
Rows Removed by Filter: 41
-> Index Scan using adroom_stat_day_adroom_id_
domain_id_url_id_is_wlabp_idx on adroom_stat (cost=0.58..25524.33 rows=491 width=16) (actual time=104.847..240.846 rows=474 loops=3043) Index Cond: ((day >= date_trunc('day'::text, (CURRENT_TIMESTAMP - '7 days'::interval))) AND (day <= date_trunc('day'::text, CURRENT_TIMESTAMP)) AND (domain_id = (unnest(adroom.domain_ids))))
Planning time: 1.580 ms
Execution time: 733331.740 ms
Dmitry Shalashov, relap.io & surfingb
ird.ru
I believe that with SSD disks random_page_cost should be very cheap, but here you go (I decided to settle on EXPLAIN without ANALYZE this time, is this is good enough?):
Sort (cost=18410.26..18410.27 rows=1 width=63)
Sort Key: (sum(st.shows)) DESC
CTE a
-> Index Scan using adroom_active_idx on adroom (cost=0.28..301.85 rows=1 width=233)
Index Cond: ((CURRENT_TIMESTAMP >= start_ts) AND (CURRENT_TIMESTAMP <= stop_ts))
Filter: (((groups -> 0) ->> 'provider'::text) ~ '^target_mail_ru'::text)
CTE b
-> HashAggregate (cost=1.28..1.29 rows=1 width=40)
Group Key: a.provider, a.id, unnest(a.domain_ids)
-> ProjectSet (cost=0.00..0.53 rows=100 width=40)
-> CTE Scan on a (cost=0.00..0.02 rows=1 width=68)
-> GroupAggregate (cost=18107.09..18107.11 rows=1 width=63)
Group Key: b.provider, d.domain
-> Sort (cost=18107.09..18107.09 rows=1 width=55)
Sort Key: b.provider, d.domain
-> Nested Loop (cost=1.00..18107.08 rows=1 width=55)
Join Filter: ((b.id = st.adroom_id) AND (b.domain_id = st.domain_id))
-> Nested Loop (cost=0.42..8.46 rows=1 width=59)
-> CTE Scan on b (cost=0.00..0.02 rows=1 width=40)
-> Index Scan using domains_pkey on domains d (cost=0.42..8.44 rows=1 width=19)
Index Cond: (id = b.domain_id)
-> Index Scan using adroom_stat_day_adroom_id_domain_id_url_id_is_wlabp_idx on adroom_stat st (cost=0.58..180
91.26 rows=491 width=16)
Index Cond: ((day >= date_trunc('day'::text, (CURRENT_TIMESTAMP - '7 days'::interval))) AND (day <= date_trunc('day'::text, CURRENT_TIMESTAMP)) AND (domain_id = d.id))
2017-11-22 17:44 GMT+03:00 Alex Ignatov <a.ignatov@xxxxxxxxxxxxxx>:
