On 1/20/18 10:13 AM, Magnus Hagander wrote: > > On Tue, Nov 28, 2017 at 2:47 AM, Michael Paquier > <michael.paquier@gmail.com <mailto:michael.paquier@gmail.com>> wrote: > > On Mon, Nov 27, 2017 at 3:28 PM, Alexander Korotkov > <a.korotkov@postgrespro.ru <mailto:a.korotkov@postgrespro.ru>> wrote: > > Attached patch atomic-pgrename-windows-1.patch fixes this problem. It > > appears to be possible to atomically replace file on Windows – ReplaceFile() > > does that. ReplaceFiles() requires target file to exist, this is why we > > still need to call MoveFileEx() when it doesn't exist. > > Do you think that it could be safer to unlink the target file first > with pgunlink()? This way you make sure that the target file is > removed and not locked. This change makes me worrying about the > introduction of more race conditions. > > Unlinking it first seems dangerous, as pointed out by Andres. > > What about first trying ReplaceFile() and then if it fails with "target > doesn't exist", then call MoveFileEx(). > > Or the other way around -- try MoveFileEx() first since that seems to > work most of the time today (if it mostly broke we'd be in trouble > already), and if it fails with a sharing violation, try ReplaceFile()? > And perhaps end up doing it something similar to what we do with shared > memory which is just to loop over it and try each a couple of time, > before giving up and failing?
This patch was mistakenly left as Needs Review during the last commitfest but it's pretty clear that a new patch is required.
