From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
Cc: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: The way to know whether the standby has caught up with the master |
Date: | 2011-05-25 14:07:21 |
Message-ID: | 4780.1306332441@sss.pgh.pa.us |
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Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> On 25.05.2011 07:42, Fujii Masao wrote:
>> To achieve that, I'm thinking to change walsender so that, when the standby
>> has caught up with the master, it sends back the message indicating that to
>> the standby. And I'm thinking to add new function (or view like
>> pg_stat_replication)
>> available on the standby, which shows that info.
> By the time the standby has received that message, it might not be
> caught-up anymore because new WAL might've been generated in the master
> already.
Even assuming that you believe this is a useful capability, there is no
need to change walsender. It *already* sends the current-end-of-WAL in
every message, which indicates precisely whether the message contains
all of available WAL data.
regards, tom lane
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