Re: Potential data loss of 2PC files

On 12/22/16 12:02 PM, Andres Freund wrote:
>
> On December 22, 2016 6:44:22 PM GMT+01:00, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> On Thu, Dec 22, 2016 at 12:39 PM, Andres Freund <andres(at)anarazel(dot)de>
>> wrote:
>>> It makes more sense of you mentally separate between filename(s) and
>> file contents. Having to do filesystem metatata transactions for an
>> fsync intended to sync contents would be annoying...
>>
>> I thought that's why there's fdatasync.
> Not quite IIRC: that doesn't deal with file size increase. All this would be easier if hardlinks wouldn't exist IIUC. It's basically a question whether dentry, inode or contents need to be synced. Yes, it sucks.

IIRC this isn't the first time we've run into this problem... should
pg_fsync() automatically fsync the directory as well? I guess we'd need
a flag to disable that for performance critical areas where we know we
don't need it (presumably just certain WAL fsyncs).
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
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