On Mon, May 27, 2019 at 05:52:13PM +0300, Konstantin Knizhnik wrote: > Postgres is opening file with FILE_SHARE_DELETE flag which makes it > possible to unlink opened file. > But unlike Unixes, the file is not actually deleted. You can see it using > "dir" command. > And stat() function also doesn't return error in this case: > > https://stackoverflow.com/questions/27270374/deletefile-or-unlink-calls-succeed-but-doesnt-remove-file > > So first check in pgwin32_safestat (r < 0) is not working at all: stat() > returns 0, but subsequent call of GetFileAttributesEx > returns 5 (ERROR_ACCESS_DENIED).
So you would basically hijack the result of GetFileAttributesEx() so as any errors returned by this function complain with ENOENT for everything seen. Why would that be a sane idea? What if say a permission or another error is legit, but instead ENOENT is returned as you propose, then the caller would be confused by an incorrect status. As you mention, what we did as of 9951741 may not be completely right, and the reason why it was done this way comes from here: https://www.postgresql.org/message-id/20160712083220.1426.58...@wrigleys.postgresql.org Could we instead come up with a reliable way to detect if a file is in a deletion pending state? Mapping blindly EACCES to ENOENT is not a solution I think we can rely on (perhaps we could check only after ERROR_ACCESS_DENIED using GetLastError() and map back to ENOENT in this case still this can be triggered if a virus scanner holds the file for read, no?). stat() returning 0 for a file pending for deletion which will go away physically once the handles still keeping the file around are closed is not something I would have imagined is sane, but that's what we need to deal with... Windows has a long history of keeping things compatible, sometimes in their own weird way, and it seems that we have one here so I cannot imagine that this behavior is going to change. Looking around, I have found out about NtCreateFile() which could be able to report a proper pending deletion status, still that's only available in kernel mode. Perhaps others have ideas? -- Michael
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