Re: checkpointer continuous flushing

On 6/20/15 2:57 AM, Fabien COELHO wrote:
>>> - as version 2: checkpoint buffer sorting based on a 2007 patch by
>>> Takahiro Itagaki but with a smaller and static buffer allocated once.
>>> Also, sorting is done by chunks of 131072 pages in the current
>>> version,
>>> with a guc to change this value.
>>
>> I think it's a really bad idea to do this in chunks.
>
> The small problem I see is that for a very large setting there could be
> several seconds or even minutes of sorting, which may or may not be
> desirable, so having some control on that seems a good idea.

ISTM a more elegant way to handle that would be to start off with a very
small number of buffers and sort larger and larger lists while the OS is
busy writing/syncing.

> Another argument is that Tom said he wanted that:-)

Did he elaborate why? I don't see him on this thread (though I don't
have all of it).

> In practice the value can be set at a high value so that it is nearly
> always sorted in one go. Maybe value "0" could be made special and used
> to trigger this behavior systematically, and be the default.

It'd be nice if it was just self-tuning, with no GUC.

It looks like it'd be much better to get this committed without more
than we have now than to do without it though...
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Data in Trouble? Get it in Treble! http://BlueTreble.com