[Zope-DB] Incomplete, unreliable results sets on Zope 2.6.3

David Woods dwoods at wcer.wisc.edu
Sun Feb 22 22:43:07 EST 2004

Thanks for your help.

I now have definitive proof that ZODBC is unreliable, at least in some
circumstances, namely the ones that apply to my site.

I created two queries, identical except that one used the ZODBC Connector
and the other used an evaluation copy of the mxODBC Connector by Egenix.
Then I set up a simple page that called both queries side by side 10 times.

Now, I mentioned in my original post that the problems we were having were
sporadic, and I tried my test page many times with no difference between the
two queries.  However, when I noticed the site having problems this evening,
I immediately called my test page.  Sure enough, the ZODBC query failed all
10 times, rturning only one of the 65 expected data rows each time, while
the mxODBC query gave correct results all 10 times.

I have no idea why any of the ZODBC queries on my site, which work correctly
most of the time, fail some of the time.  It doesn't appear to be related to
load or any sort of data caching, or anything else I can determine.  But I
now have evidence that ZODBC does fail sometimes when mxODBC doesn't, and
that's enough to convince me that the problems I have been experiencing are
due to the ZODBC Connector.  I guess Egenix will be getting an order from us
tomorrow morning.

David Woods, Ph.D.
STELLAR Web Master and Lead Developer
Wisconsin Center for Education Research
University of Wisconsin, Madison

-----Original Message-----
From: Dieter Maurer [mailto:dieter at handshake.de]
Sent: Saturday, February 21, 2004 2:00 PM
To: David Woods
Cc: zope-db at zope.org
Subject: Re: [Zope-DB] Incomplete, unreliable results sets on Zope 2.6.3

David Woods wrote at 2004-2-20 14:06 -0600:
> ... partial results; Zope 2.3.2 works fine, Zope 2.6.3 not ...
>Since the move to the new server, though, we've had sporadic problems with
>getting incomplete data from the queries.  For example, a query that should
>get a list 65 students for a particular course from the database might get
>all 65, but it might get 8 or 1 or 17 or 62 instead.  Zope acts like it's
>just gotten all the data it should have and just carries on.

There was no significant change in this areas between Zope 2.3 and
Zope 2.6.

At your place, I would drop ZODBCA in favour of "ZmxODBCDA" (commercial,
but reasonably priced) and see whether the problem disappears.
There are several issues known for ZODBCDA (although nothing like
you observed...)


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