Обсуждение: auto_explain and parallel queries issue
Hi
I am testing PostgreSQL in customer's environment and I found some unexpected behave.arallel worker for PID 20089 : auto_explain database=NULL client=local appname=psql
arallel worker for PID 20089 : duration: 121.250 ms plan:
arallel worker for PID 20089 : Query Text: select sum(a) from bigtable group by b;
arallel worker for PID 20089 : Partial HashAggregate (cost=10675.00..10774.59 rows=9959 width=12)
arallel worker for PID 20089 : Group Key: b
arallel worker for PID 20089 : -> Parallel Seq Scan on bigtable (cost=0.00..8591.67 rows=416667 width=8)
arallel worker for PID 20089 : auto_explain database=NULL client=local appname=psql
arallel worker for PID 20089 : duration: 128.247 ms plan:
arallel worker for PID 20089 : Query Text: select sum(a) from bigtable group by b;
arallel worker for PID 20089 : Partial HashAggregate (cost=10675.00..10774.59 rows=9959 width=12)
arallel worker for PID 20089 : Group Key: b
arallel worker for PID 20089 : -> Parallel Seq Scan on bigtable (cost=0.00..8591.67 rows=416667 width=8)
res [local] SELECT: auto_explain database=postgres client=[local] appname=psql
res [local] SELECT: duration: 149.478 ms plan:
res [local] SELECT: Query Text: select sum(a) from bigtable group by b;
res [local] SELECT: Finalize HashAggregate (cost=13865.98..13965.57 rows=9959 width=12)
res [local] SELECT: Group Key: b
res [local] SELECT: -> Gather (cost=11675.00..13766.39 rows=19918 width=12)
res [local] SELECT: Workers Planned: 2
res [local] SELECT: -> Partial HashAggregate (cost=10675.00..10774.59 rows=9959 width=12)
res [local] SELECT: Group Key: b
res [local] SELECT: -> Parallel Seq Scan on bigtable (cost=0.00..8591.67 rows=416667 width=8)
On 04/16/2018 09:25 AM, Pavel Stehule wrote: > Hi > > I am testing PostgreSQL in customer's environment and I found some > unexpected behave. > > When auto_explain is used, and there is slower parallel query, then > auto_explain raises log for any slow process. > FWIW this is the same issue that I reported in 2016: https://www.postgresql.org/message-id/3f62f24e-51b3-175c-9222-95f25fd2a9d6%402ndquadrant.com regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
2018-04-16 10:33 GMT+02:00 Tomas Vondra <tomas.vondra@2ndquadrant.com>:
On 04/16/2018 09:25 AM, Pavel Stehule wrote:
> Hi
>
> I am testing PostgreSQL in customer's environment and I found some
> unexpected behave.
>
> When auto_explain is used, and there is slower parallel query, then
> auto_explain raises log for any slow process.
>
FWIW this is the same issue that I reported in 2016:
https://www.postgresql.org/message-id/3f62f24e-51b3-175c- 9222-95f25fd2a9d6% 402ndquadrant.com
yes. The fix should not be too hard. The report can do only process who owns query text
Regards
Pavel
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services