Use a different strategy if we are close to one domain per record.
It will use combined multiple domain at once instead of doing one query for
almost each record validated.
issue6983
review39021002
This is a valid depends value for a field but the __init__ method lose the
second _parent_ once it has been instantiated a first time.
Setting _parent_ value must be done recursively.
issue6441
review40261002
The method set_context does not replace the context but just update it.
So we could have leak of the surrounding into the read context.
issue5614
review25161002
We need to loop to compare the values instead of using a dictionary because the
values are not necessary hashable. But it is still an improvement compared to
calling the set method for each record.
issue5398
review19111002
Cédric Krier