[Zope] problem migrating ZClasses from Zope 2.6.1 to Zope 2.9.8

[Jonathan]

----- Original Message ----- 
From: "Allen Schmidt Sr." <aschmidt at fredericksburg.com>
To: "Jens Vagelpohl" <jens at dataflake.org>
Cc: "zope user list" <zope at zope.org>
Sent: Wednesday, March 26, 2008 7:59 AM
Subject: Re: [Zope] problem migrating ZClasses from Zope 2.6.1 to Zope 2.9.8


> That sounds so easy. We have one ZClass but it is the basis of almost our 
> entire newspaper website. The news ZClass was built in 2000 and put into 
> production when we went live on Zope in Feb 2001 (just before the guys at 
> Zope Corp said that ZClasss were bad). Over 7 full years of daily news as 
> ZClass objects. We are in the same boat as we want to move from 2.7.5 to a 
> later version. We could switch to SQL articles but then we would have to 
> make sure all the old URLs still functioned as our content is all over the 
> search engines...and convert everywhere there are tools to manage story 
> creation, importing, editing, etc. Yuck. We could just make the cutover 
> one day and just keep an instance running for the old stuff and all new 
> stuff runs from SQL.

We did a similar conversion product, but instead of switching to SQL we just 
build new python-based class instance objects, so that all existing urls 
would continue to work.  We built the new class instances in a separate 
folder, keeping the same ids as the original zclass instances, and then just 
swapped the folders around.  We are using zcatalogs, so we also had to 
rebuild these.

We had to manually create a very simple zope product to define the new 
classes, but this is a very easy/simple process.  We then used a combination 
of python scripts and external methods to loop thru the zclass instances, 
create new python-based class instances and update the new zcatalogs (we had 
5 different sets of data each with its own zcatalog).

All-in-all it was a bit of a pita, but the ability to upgrade to newer zope 
versions without fear was well worth the time and effort.

Jonathan