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

Fujii Masao <masao.fujii@gmail.com>

From: Fujii Masao <masao.fujii@gmail.com>

To: Robert Haas <robertmhaas@gmail.com>

Cc: Simon Riggs <simon@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2011-03-11T10:46:03Z

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Efficient transaction-controlled synchronous replication.
- a8a8a3e09652 9.1.0 cited

On Fri, Mar 11, 2011 at 5:04 AM, Robert Haas <robertmhaas@gmail.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