Re: Regarding Checkpoint Redo Record

On Wed, Jan 4, 2012 at 11:02 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On Wed, Jan 4, 2012 at 3:56 PM, Heikki Linnakangas
> <heikki.linnakangas@enterprisedb.com> wrote:
>> On 04.01.2012 08:42, Amit Kapila wrote:
>>>
>>> Why PostgreSQL needs to write WAL record for Checkpoint when it maintains
>>> same information in pg_control file?
>>
>>
>> I guess it wouldn't be strictly necessary...
>
> Apart from replicated standbys, which need that info for running restartpoints.

Yeah.

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.  I
assume there's some reason that doesn't work, I just don't know what
it is...

-- 
Robert Haas
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