Re: ZODB writes on startup - why?

Paul Winkler wrote:

> Over on zope-dev I've been trying to get a Zope 2.7.0 instance to
> start with a read-only storage. Zope fails during product
> initialization *only* if I've got Formulator installed.

> I've traced this to FieldRegistry.initializeFieldForm().
> I've never looked at the Formulator code before today,
> so I'm probably misunderstanding all kinds of things...
> but my first question is about these lines:
> 
> def initializeFieldForm(field_class):
>     """Initialize the properties (fields and values) on a particular
>     field class. Also add the tales and override methods.
>     """
>     ...
>     form = BasicForm()
>     override_form = BasicForm()
>     tales_form = BasicForm()
>     ...
>     field_class.form = form
>     field_class.override_form = override_form
>     field_class.tales_form = tales_form
> 
> BasicForm inherits from Persistent.
> I think this is my problem.  initializeFieldForm()
> gets called many times during product initialization,
> because it's called by FieldRegistry.FieldRegistry.registerField.
> 
> Knowing only this much, I don't understand why form, override_form,
> and tales_form need to be persistent. Do they ever change
> after startup?  AFAICT, they get recreated every time you restart zope! 
> Isn't that just pointless ZODB bloat?  
> 
> If BasicForm needs to derive from Persistent for some other reason,
> might it be possible to refactor a bit and use a non-persistent
> relative of BasicForm for field_class.form, et al?

I'm not sure I am misunderstanding you here, even though BasicForm() is 
derived from persistent, they're attached to *classes* here, and since 
these classes aren't (and can't be) persistent I'd think these 
attributes never end up in the ZODB.

Regards,

Martjin