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Re: When to use Berkeley transactions.

From: Greg Hudson <ghudson_at_MIT.EDU>
Date: 2003-02-21 06:13:15 CET

On Thu, 2003-02-20 at 21:20, Karl Fogel wrote:
> For example, imagine a checkout without transactions:
[Failure scenario involving the reps/strings table indirection]

This is an interesting weakness of Berkeley DB relative to the
filesystem as a storage tool for large data objects.

We have separate reps and strings tables so that we can have a stable
reference point for the representation while we build up a new string
entry in several steps (specifically, during redeltification). If we
didn't have separate tables, then the contents of a revision would
always be valid, and we wouldn't need to lock around read operations.

In the filesystem, you can build up a file in several steps and rename
it into place (at least on Unix, and I think also on Windows), without
changing the reference point.

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Received on Fri Feb 21 06:13:58 2003

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