From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Amit Kapila <amit(dot)kapila(at)huawei(dot)com>, PG Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Regarding Checkpoint Redo Record |
Date: | 2012-01-04 21:26:47 |
Message-ID: | CA+TgmoZC=oijDYkWtg3dBX+ZcXFy-Wfeu3QDD8rJbpkJ71TRtA@mail.gmail.com |
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Lists: | pgsql-hackers |
On Wed, Jan 4, 2012 at 4:06 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> But, the OP makes me wonder: why can a standby only perform a
>> restartpoint where the master performed a checkpoint? It seems like a
>> standby ought to be able to create a restartpoint anywhere, just by
>> writing everything, flushing it to disk, and update pg_control.
>
> Perhaps, but then crash restarts would have to accept start pointers
> that point at any random place in the WAL. I like the additional error
> checking of verifying that there's a checkpoint recod there.
I could go either way on that one, but...
> Also
> I think the full-page-write mechanism would no longer protect against
> torn pages during replay if you did that.
...this is a very good point.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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