Re: fsync-pgdata-on-recovery tries to write to more files than previously

On 05/26/2015 08:05 AM, Robert Haas wrote:
> On Mon, May 25, 2015 at 9:54 PM, Stephen Frost <sfrost@snowman.net> wrote:
>> I certainly see your point, but Tom also pointed out that it's not great
>> to ignore failures during this phase:
>>
>> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
>>> Greg Stark <stark@mit.edu> writes:
>>>> What exactly is failing?
>>>> Is it that fsync is returning -1 ?
>>> According to the original report from Christoph Berg, it was open()
>>> not fsync() that was failing, at least in permissions-based cases.
>>>
>>> I'm not sure if we should just uniformly ignore all failures in this
>>> phase.  That would have the merit of clearly not creating any new
>>> startup failure cases compared to the previous code, but as you say
>>> sometimes it might mean ignoring real problems.
>> If we accept this, then we still have to have the lists, to decide what
>> to fail on and what to ignore.  If we're going to have said lists tho, I
>> don't really see the point in fsync'ing things we're pretty confident
>> aren't ours.
> No, that's not right at all.  The idea, at least as I understand it,
> would be decide which errors to ignore by looking at the error code,
> not by looking at which file is involved.
>


OK, I'm late to the party. But why exactly are we syncing absolutely 
everything? That seems over-broad.

And might it be better to check that we can open each file using 
access() than calling open() and looking at the error code?

cheers

andrew