Re: BUG #13484: Performance problem with logical decoding

From: olivier(dot)gosseaume(at)free(dot)fr
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #13484: Performance problem with logical decoding
Date: 2015-07-06 20:58:29
Message-ID: 542422208.17082311.1436216309004.JavaMail.root@zimbra72-e12.priv.proxad.net
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>> To be more concise :
>> - ONE transaction with 4095 operations -> consumed in 80mS
>> - TEN transactions with 4095 operations each (so 40950 operations) -> 380mS (which as you said is very good -less than linear growth-)
>> - ONE transaction with 4096 operations -> consumed in 4204mS (ouch ...). I confirm there are only 4096 changes in one transaction
>> - TEN transactions with 4095 operations each (so 40950 operations) -> 34998mS, ouch again
>
>Given the third result it's unlikely, but just to make sure: Are you
>sure network issues aren't a factor here? 40950 changes are about 3.8MB,
>over a slow network that can take a second. Additionally psql will
>display all the changes in a pager, which'll not be fast either (but
>shouldn't be included in \timing's output).

I'm doing everything on the same host, so network is not involved at all (localhost)

br
Olivier

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