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Re: Merge tracking: will SQLite make NFS sad?

From: Malcolm Rowe <malcolm-svn-dev_at_farside.org.uk>
Date: 2007-03-05 18:59:53 CET

On Mon, Mar 05, 2007 at 09:15:30AM -0500, Mark Phippard wrote:
> On 3/5/07, David Glasser <glasser@mit.edu> wrote:
> >My impression (which may be out of date) is that sqlite2 used only
> >file-level locking (like fsfs), but sqlite3 uses byte-level locking.
> >I don't know much about NFS, but this is certainly bad for AFS at
> >least.

I don't know about sqlite2, but yes, that's my understanding of sqlite3
too. FSFS only uses whole-file byte-range locks (which are a special
case of POSIX fcntl() locks).

> If the database writes are all being serialized at a higher level by fsfs
> (meaning it ensures that only one transaction at a time is being written)

FSFS ensures that only one transaction is being committed at one time -
are you doing the SQLite writes under the fs-wide write-lock?

> does that insulate us from problems at all? Or does the fact that other
> client might be reading the database mean that corruption could happen? I
> would assume it at least means that incorrect answers could be returned.

Hence my question.

Regards,
Malcolm

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Received on Mon Mar 5 19:00:20 2007

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