> Or a
field schema_version that's increased with each installed
> patch?
>
I was thinking along the same lines, but something a bit more general. A
site_props table, with key-value pairs. It would be like objectcache but
guaranteed persistent, and it could be used to hold things such as a
boolean value showing when the update in question is applied.
I prefer that idea.
A version number requires that patches be
installed in a particular order, which could cause problems
(especially if 2 patches are being developed simultaneously). I don't
think a boolean value would be required - just the existence of the
row would be enough.
You may have versions of the same sub-schema.