Re: Batch replication ordering (was Re: [GENERAL] 32/64-bit transaction IDs?)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Ed L(dot)" <pgsql(at)bluepolka(dot)net>
Cc: pgsql-general(at)postgresql(dot)org, Steven Singer <ssinger(at)navtechinc(dot)com>
Subject: Re: Batch replication ordering (was Re: [GENERAL] 32/64-bit transaction IDs?)
Date: 2003-04-10 22:11:18
Message-ID: 7109.1050012678@sss.pgh.pa.us
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"Ed L." <pgsql(at)bluepolka(dot)net> writes:
> On Saturday March 22 2003 12:00, Tom Lane wrote:
>> Note that all of a transaction's updates will become visible in the
>> pending-update table simultaneously when it commits, so (as long as
>> you grab batches in single SELECTs, or with a serializable transaction)
>> there's no problems with partial transactions being applied by a batch.

> If you grab everything in the queue with a single SELECT, this works.
> Depending on the queue length, that's not always practical, and as noted
> above, committed batches could result in partial transactions on the slave.
> So the riddle is how to get a consistent but batchable replication order.

You don't have to do anything special if you pull the contents of a
batch in a single serializable transaction. I see no reason to think
that using a serializable transaction is "hammering the master"; so
you are asking for a solution to a non-problem.

regards, tom lane

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