Re: BUG #12910: Memory leak with logical decoding

From: Peter Slavov <pet(dot)slavov(at)gmail(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #12910: Memory leak with logical decoding
Date: 2015-04-06 14:55:44
Message-ID: 55229E70.3040305@gmail.com
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Hi Andres,

Thanks for the answer, and happy holidays

На 6.04.2015 в 16:50, Andres Freund написа:
> Hi,
>
> I'm on holidays right now, so my answers will be delayed.
>
> On 2015-04-06 15:35:19 +0300, Peter Slavov wrote:
>> Before I start I can see that the pg_xlog directory is 7.2 GB size.
>> This give me some idea that the size of the changes cannot be much bigger
>> than that.
> There's no such easy correlation. That said, there pretty much never
> should be a case where so much memory is needed.
>
>> After I start ti get the transactions changes one by one with select * from
>> pg_logical_slot_get_changes('<slot name>', null, 1),
> As I said before, it's *not* a good idea to consume transactions
> one-by-one. The startup of the decoding machinery is quite expensive. If
> you want more control about how much data you get you should use the
> streaming interface.
I tried with more transactions or without limit there but there is no
difference.
I actually tried before with pg_recvlogical, which is actually using the
streaming interface,
but the result was exactly the same. My guess is that the problem is in
the plug-in actualy..
>> Maybe I am not understanding something, but is this normal?
> It's definitely not normal. It's unfortunately also hard to diagnose
> based on the information so far. Any chance you can build a reproducible
> test case?
Yes I will try to make a test case that is reproducible.
>
> Greetings,
>
> Andres Freund

Thanks,
Peter Slavov

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