Re: Query became very slow after 9.6 -> 10 upgrade - Mailing list pgsql-performance

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@gmail.com]
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.

 

Query: https://pastebin.com/9b953tT7

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 & surfingbird.ru