Re: Proposing pg_hibernate

On 6/4/14, 8:56 AM, Andres Freund wrote:
> On 2014-06-04 09:51:36 -0400, Robert Haas wrote:
>> >On Wed, Jun 4, 2014 at 2:08 AM, Andres Freund<andres(at)2ndquadrant(dot)com> wrote:
>>> > >On 2014-06-04 10:24:13 +0530, Amit Kapila wrote:
>>>> > >>Incase of recovery, the shared buffers saved by this utility are
>>>> > >>from previous shutdown which doesn't seem to be of more use
>>>> > >>than buffers loaded by recovery.
>>> > >
>>> > >Why? The server might have been queried if it's a hot standby one?
>> >
>> >I think that's essentially the same point Amit is making. Gurjeet is
>> >arguing for reloading the buffers from the previous shutdown at end of
>> >recovery; IIUC, Amit, you, and I all think this isn't a good idea.
> I think I am actually arguing for Gurjeet's position. If the server is
> actively being queried (i.e. hot_standby=on and actually used for
> queries) it's quite reasonable to expect that shared_buffers has lots of
> content that is*not* determined by WAL replay.

Perhaps instead of trying to get data actually into shared buffers it would be better to just advise the kernel that we think we're going to need it? ISTM it's reasonably fast to pull data from disk cache into shared buffers.

On a related note, what I really wish for is the ability to restore the disk cash after a restart/unmount...
--
Jim C. Nasby, Data Architect jim(at)nasby(dot)net
512.569.9461 (cell) http://jim.nasby.net