Martynas Brijunas added the comment:
Hi Steve, Eryk,
thank you very much for looking into this. I was looking into "st_ino"
as a potential substitute of a full path of a file when it comes to
uniquely identifying that file in a database.
> ReFS uses a 128-bit file ID, which I gather consists of a 64-bit directory ID
> and a 64-bit relative ID. (Take this with a grain of salt. AFAIK, Microsoft
> hasn't published a spec for ReFS.) The latter is 0 for the directory itself
> and increments by 1 for each file created in the directory, with no reuse of
> previous values if a file is deleted or moved. If that's correct, and if
> "test.jpg" was created in "\test", then the directory ID of "\test" is
> 0x29d5, and the relative file ID is 0x4ae.
This assumption seems to be correct. All files within the same
directory have identical first half of their ID, as reported by
"fsutil".
U:\test>fsutil file queryfileid test.jpg
File ID is 0x29d504ae
U:\test>fsutil file queryfileid test.nef
File ID is 0x29d50483
U:\test>fsutil file queryfileid test.ARW
File ID is 0x29d50484
U:\test>fsutil file queryfileid test.db
File ID is 0x29d50495
>
> > >>> from pathlib import Path
> > >>> hex(Path('U:/test/test.jpg').stat().st_ino)
> > '0x44ae29d5'
>
> os.stat calls WINAPI GetFileInformationByHandle, which returns a 64-bit file
> ID. It appears that ReFS generates this ID by concatenating the relative ID
> and directory ID in a way that is "not guaranteed to be unique" according to
> the BY_HANDLE_FILE_INFORMATION [1] docs.
The feedack from "st_ino" appears to be in total sync with "fsutil".
The only real difference (apart for the for the missing leading zeros
in each half) is the inclusion of a hex "4" at the very beginning of
the hex sequence. But even that is consistent as the "4" is present in
all cases.
>>> hex(Path('U:/test/test.jpg').stat().st_ino)
'0x44ae29d5'
>>> hex(Path('U:/test/test.nef').stat().st_ino)
'0x448329d5'
>>> hex(Path('U:/test/test.arw').stat().st_ino)
'0x448429d5'
>>> hex(Path('U:/test/test.db').stat().st_ino)
'0x449529d5'
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