Re: Remove lower limit on checkpoint_timeout?

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Remove lower limit on checkpoint_timeout?
Date: 2016-12-23 14:28:51
Message-ID: alpine.DEB.2.20.1612231519560.3892@lancre
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Hello Andres,

> for testing - like yesterday's 6ef2eba3f - it's annoying that
> checkpoint_timeout has 30s minimum. I've now locally patched that to be
> 1s a significant number of times.
>
> While it's not a particularly good idea to set it to 1s on a production
> system, I don't see why we need to prevent that. It's not like 30s is
> likely to be a good idea either.
>
> Hence I'd like to set the lower limit to 1s.

My 0.02€:

I have also resorted to reduce this limit in order to reduce latency and
avoid postgres freezing on checkpoints, before checkpoint buffers where
sorted. I think I may have tried down to 0.1s which involved some changes,
and it worked quite well for the purpose.

So basically I would also be in favor to reduce the lower limit down to 1
second, maybe with a warning output when set to low values, say under 1
minute, as you propose.

--
Fabien.

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