Re: Batch replication ordering (was Re: [GENERAL] 32/64-bit

From: "Ed L(dot)" <pgsql(at)bluepolka(dot)net>
To: Steven Singer <ssinger(at)navtechinc(dot)com>
Cc: Jan Wieck <JanWieck(at)Yahoo(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <pgsql-general(at)postgresql(dot)org>
Subject: Re: Batch replication ordering (was Re: [GENERAL] 32/64-bit
Date: 2003-04-13 16:06:35
Message-ID: 200304131006.35190.pgsql@bluepolka.net
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On Sunday April 13 2003 9:48, Steven Singer wrote:
> >
> > nothing wrong with that necessarily, unless you wanted to update the
> > master bookkeeping on every new xid as well, in which case it would
> > defeat my purpose in the master batch.
>
> Why do you need to update the master after every commit on the slave? If
> your storing the last seqid sent to the slave on that slave(you would
> have to update this during every transaction on the slave but I don't see
> this as a big deal) and you use that value as the authoratative value for
> deciding what next to send to the slave.

Agreed, I don't think you need to update the master after every commit on
the slave. On the contrary, I was simply making the observation that it
would not be useful to do so with respect to performance and traffic.

> You would have to periodically update the master to tell it that a
> tranaction can be removed form the replication_queue but this can be done
> periodically(every x transactions). If dbmirror goes down in between a
> commit on the slave and the master being updated then the transactions
> will stay on the master in the queue until dbmirror comes back up at
> which point it will see from the slave that the transactions have been
> sent and they don't need to be resent. Then the master can be updated so
> those rows can be cleaned from the queue.

Agreed, exactly.

Ed

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