[ZODB-Dev] mvcc related error?

Chris Withers chris at simplistix.co.uk
Fri Mar 16 04:45:04 EDT 2007

Jeremy Hylton wrote:
> transaction end committed.  If end is None, it implies that the
> revision returned by loadBefore() is the current revision.  There is
> an assert here, because the _setstate_noncurrent() is only called if
> the object is in the invalidated set, which implies that there is a
> non-current revision to read.

Is there any way an object could be invalidated without there being a 
non-current revision to read?
What are the possible causes of invalidation?

> If I had to guess, I'd say it was a bug in loadBefore().  It looks
> like the only ways for loadBefore() to return None for end are
> - The very first record for the object has a transaction id less than
> the tid argument.  If so, end_tid is never set.  Not sure this is
> compatible with the object being in the invalidated set.

Since I'm not using versions, this is where I'd point the finger.

> Perhaps the reasoning about invalidated sets and transaction ids is
> wrong in the presence of versions.  

Well, there are no versions here, so I can't help with that ;-)



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