Re: Error with index on unlogged table

On Wed, Dec 9, 2015 at 8:04 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2015-12-09 19:36:11 +0900, Michael Paquier wrote:
>> On Wed, Dec 9, 2015 at 4:41 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> > On 2015-12-09 16:30:47 +0900, Michael Paquier wrote:
>> >> > I'm kinda wondering if it wouldn't have been better to go through shared
>> >> > buffers in ResetUnloggedRelationsInDbspaceDir() instead of using
>> >> > copy_file().
>> >>
>> >> For deployment with large shared_buffers settings, wouldn't that be
>> >> actually more costly than the current way of doing? We would need to
>> >> go through all the buffers at least once and look for the INIT_FORKNUM
>> >> present to flush them.
>> >
>> > We could just check the file sizes on disk, and the check for the
>> > contents of all the pages for each file.
>>
>> By doing it at replay, the flushes are spread across time. And by
>> doing it at the end of recovery, all the flushes would be grouped. Do
>> you think that's fine?
>
> The point is that we'd no flushes, because the data would come directly
> from shared buffers...

Oh, OK. I didn't read though your lines correctly. So you basically
mean that we would look at the init files that are on disk, and check
if they are empty. If they are, we simply use XLogReadBufferExtended
to fetch the INIT_FORKNUM content and fill in another buffer for the
MAIN_FORKNUM. More or less right?
--
Michael