Re: Non-pausing table scan on 9.6 replica?

From: Mark Fletcher <markf(at)corp(dot)groups(dot)io>
To: Andreas Kretschmer <andreas(at)a-kretschmer(dot)de>
Cc: pgsql-general(at)lists(dot)postgresql(dot)org
Subject: Re: Non-pausing table scan on 9.6 replica?
Date: 2019-03-06 05:41:06
Message-ID: CAEO096o5O10_04Z-QKbpHi6rsteSHScw+7GCc5YEb+YXko_FzA@mail.gmail.com
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Thank you for responding to my email.

On Tue, Mar 5, 2019 at 9:20 PM Andreas Kretschmer <andreas(at)a-kretschmer(dot)de>
wrote:

>
> have you set ```max_standby_streaming_delay``? The default is 30
> seconds, which means that this will be the maximum time allowed for a
> replication lag caused by a conflicting query.
>

Yes, we've bumped that up a lot.

> You can use ``hot_standby_feedback = on``, but the downside will be more
> bloat on the tables.
>
> I'm not sure I understand. I'm not worried about the query being cancelled
on the replica. max_standby_streaming_delay fixes that for us. I'm worried
about the streaming replication being paused while this table scan is
running. If the table scan takes several minutes, then the replica becomes
several minutes out of sync with the master. I'd prefer that not to happen
and I'm wondering if there's a way to do that.

Thanks,
Mark

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