IS_IN_DB - Label

[Alex]

It is possible to use several items in IS_IN_DB label, but how to use
column name from refrence table?

For example 3 tables:

type_class (type_class_name)
type (type_class_id, type_name)
detail (type_id, detail_name)

I can do for "requires" in detail table this:
requires=IS_IN_DB(db, 'type.id', '%(type_name)s'

but how can i include 'type_class_name' there?
like:
requires=IS_IN_DB(db, 'type.id', '%(type_class_id.type_class_name) ---
%(type_name)s'
or
requires=IS_IN_DB(db, 'type.id', '%(type_class_name) --- %(type_name)s'

[mdipierro]

No. We have discussed implementing this. The problem is that the only
efficient way to do this is via a join. Without a join it would be
slow. By using a join it would not work on GAE. To make it efficient
on GAE one would have to denormalize or cache them. I think these are
important design issues I am not convinced they should he hidden from
the developer into a validator. I am not sure there is one size fit
all. Hiding too much logic into the validator would result in too many
people complaining that this is not doing quite what they expect.

Anyway, you can design your own validator that does it without need to
modify web2py. Once we have such validator, if there is overwhelming
support for it, we can include it in web2py or replace the existing
IS_IN_DB.

Massimo