Re: Checkpointer on hot standby runs without looking checkpoint_segments

On 8 June 2012 15:21, Robert Haas <robertmhaas@gmail.com> wrote:
> On Fri, Jun 8, 2012 at 9:58 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
>> On 8 June 2012 14:47, Robert Haas <robertmhaas@gmail.com> wrote:
>>
>>>> ISTM that we should avoid triggering a checkpoint on the master if
>>>> checkpoint_segments is less than wal_keep_segments. Such checkpoints
>>>> serve no purpose because we don't actually limit and recycle the WAL
>>>> files and all it does is slow people down.
>>>
>>> On the other hand, I emphatically disagree with this, for the same
>>> reasons as on the other thread.  Getting data down to disk provides a
>>> greater measure of safety than having it in memory.  Making
>>> checkpoint_segments not force a checkpoint is no better than making
>>> checkpoint_timeout not force a checkpoint.
>>
>> Not sure which bit you are disagreeing with. I have no suggested
>> change to checkpoint_timeout.
>
> You already made it not a hard timeout.  We have another nearby thread
> discussing why I don't like that.
>
>> What I'm saying is that forcing a checkpoint to save space, when we
>> aren't going to save space, makes no sense.
>
> We are also forcing a checkpoint to limit recovery time and data loss
> potential, not just to save space.

Nothing I've said on this thread is related to the other thread.
Please don't confuse matters.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services