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Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication.

From: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication.
Date: 2011-03-11 10:46:03
Message-ID: AANLkTi=f+EtkPU+rRgz=Ay-X80OvCGvxK_O6LpL9_dss@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackers
On Fri, Mar 11, 2011 at 5:04 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>>        if ((wrote_xlog && XactSyncCommit) || forceSyncCommit || nrels > 0 ||
>> SyncRepRequested())
>>
>> Whenever synchronous_replication is TRUE, we disable synchronous_commit.
>> But, before disabling that, we should check also max_wal_senders and
>> synchronous_standby_names? Otherwise, synchronous_commit can
>> be disabled unexpectedly even in non replication case.
>
> Yeah, that's bad.  At the risk of repeating myself, I don't think this
> code should be checking SyncRepRequested() in the first place.  If the
> user has turned off synchronous_commit, then we should just commit
> asynchronously, even if sync rep is otherwise in force.  Otherwise,
> this if statement is going to get really complicated.   The logic is
> already at least mildly wrong here anyway: clearly we do NOT need to
> commit synchronously if the transaction has not written xlog, even if
> sync rep is enabled.

Yeah, not to wait for replication when synchronous_commit is disabled
seems to be more reasonable.

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

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