Re: BUG #14635: Query is executed slower on hot standby slave database then on master database

On Fri, Apr 28, 2017 at 11:38 PM, <vgomenyuk(at)callfire(dot)com> wrote:

> The following bug has been logged on the website:
>
> Bug reference: 14635
> Logged by: Vitaliy Gomenyuk
> Email address: vgomenyuk(at)callfire(dot)com
> PostgreSQL version: 9.2.14
> Operating system: CentOS 6
> Description:
>
> Hello,
>
> We have two equal servers (CPU, RAM, HDD).
> We are using Postgresql 9.2.14 currently.
> Have setup master-slave streaming replication.
>
> Running next query at master and slave databases:
> explain analyze SELECT "om".* FROM "Table" AS "om" WHERE (om."UserID" =
> 11111) AND (NOT om."Deleted") AND (om."Status" = 0) ORDER BY "StampToSend"
> asc LIMIT 11;
> An execution plans are the same on master and slave databases.
>
> An execution time on master database: 138.116 ms
> An execution time on hot standby slave database with working replication:
> 1623.496 ms
> An execution time on slave database with turned off replication (after
> creating trigger file): 132.354 ms (equal to an execution time on master
> database).
>
> Why there is so huge difference in execution time between Postgresql with
> and without working streaming replication?
> How to improve the situation: to make an execution time on Hot standby
> slave
> dtabase with working replication equeal to master database?
>

Is the issue happening always or only sometimes?
can you please check explain plan output on both the machines with verbose
and buffers options.

explain (analyze, verbose, buffers) /*query*/

The explain output may help in identifying the plan of the query where it
is taking
more time compared to master.

Regards,
Hari Babu
Fujitsu Australia