On Wednesday, March 15, 2017 at 12:03:52 PM UTC-4, Richard wrote:
>
> We can even use a set inside an IS_IN_DB() requires inside model
> definition something like that prevent model from being lazy :
>
> db.define_table('tablename',
> Field('fk_id_field', 'reference othertable',
> requires=IS_IN_DB(db(
> db.othertable.id > 0), 'othertable.id', '%(represent_field)s')
> )
> )
>
> This is sad...
>
> I confirm that
>
> some_set = db(db.tablename.fieldname > 1)
>
> put in model outside of table definition prevent the table over which the
> set point from being lazy...
>
> And use of set inside IS_IN_DB() also prevent table from being lazy
>
The point of lazy tables is that they are not fully defined until you
*reference
*them (i.e., via db.mytable or db['mytable']). Of course, once you
reference them, they must be defined. If something like db.tablename.fieldname
> 1 would not trigger a table to be defined, what exactly would you expect
to trigger the definition?
Anyway, the exact case you mention is covered by the on_define
<http://web2py.com/books/default/chapter/29/06/the-database-abstraction-layer#on_define>
argument.
If you want to improve performance related to model instantiation, you
should also consider conditional models as well as moving some model
definitions to modules.
Anthony
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