Re: Schema provider/CA lookup status

Hi Martin

> So what is a valid hash?

We used the id() of the schema as the hash, as a stopgap measure. This only
works if any methods that modify the schema also invalidate the cache. We
haven't done this yet.

A valid hash could be the id(schema) plus the modification date of the schema.
A modified schema will cause a cache miss, which is correct.

The old one won't be flushed, though. The __dict__-based implementation doesn't
flush old schemas either. Schemas don't change that often, but it's still ugly
to carry around a bunch of stale cached schemas between Zope restarts.

> And why exactly is this hash causing cache misses? Is __dict__ not stable
> enough?

AFAIR the cache misses we saw were legit. If the schema changes, it isn't found
in the cache. So the __dict__ is stable and thorough. It's just slooooooooow,
because it uses all the field objects on the schema, and all the properties of
each field.

-- 
jean

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