Re: Slow temporary tables when using sync rep

Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>

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From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>

To: Michael Nolan <htfoot@gmail.com>

Cc: Thom Brown <thom@linux.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2012-04-17T10:30:03Z

Lists: pgsql-hackers

Attachments

temp-rel-syncrep-flush-1.patch (text/x-diff) patch

On 17.04.2012 02:54, Michael Nolan wrote:
> On Mon, Apr 16, 2012 at 6:27 PM, Thom Brown<thom@linux.com>  wrote:
>
>> Hi,
>>
>> I've noticed that when using synchronous replication (on 9.2devel at
>> least), temporary tables become really slow:
>
> Since temporary tables are only present until the session ends (or
> possibly only until a commit), why are they replicated at all?

They're not replicated.

What happens is that we write the commit record if the transaction 
accesses a temporary table, but we don't flush it. However, we still 
wait until it's replicated to the standby. The obvious fix is to not 
wait for that, see attached.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com