On Aug 3, 2015 3:36 AM, "Anssi Kääriäinen" <akaar...@gmail.com> wrote: > > On Wednesday, July 29, 2015 at 8:05:10 AM UTC+3, Aron Podrigal wrote: >> >> I would like to propose making Fields.default to rely on the database generated defaults where possible. This could be implemented by having some constants like fields.CURRENT_TIMESTAMP, etc. The tricky part here is to detect database backend specific capabilities and have a python equivalent fallback. >> >> Any thoughts? > > > A couple of questions about this: > - What should happen when you instantiate a new model with DB default, and show that model to the user in a form. Is the field shown to the user, and if so, what value should it have?
The field would have no value, so when displayed on the form it would be blank. A field with blank=False which is included in a form, having a db_default would be useless. > - How to implement actual fetching of the values after save() - PostgreSQL supports RETURNING, but this is not the case for all databases. The value would be fetched on demand on its first access, saving a trip to the database if the field is not accessed. Subsequent updates on that instance would leave out that field from the list of fields to be updated, unless its value has been changed on the instance. Maybe we can allow to handle this based on some parameter provided to save() ? > - When is the default applied? On first save of the model, or on model init time? Of course on first save, as we want the default value atomically within the same transaction. > - Do we want to allow extending this to defaults that are applied on every save (automatic database backed modified timestamps for example)? +1 for this one too. > > - Anssi > > -- > You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. > To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. > To post to this group, send email to django-developers@googlegroups.com. > Visit this group at http://groups.google.com/group/django-developers. > To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/f1a7cc68-de1a-49f8-bdf8-ebfaade59955%40googlegroups.com . > > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. To post to this group, send email to django-developers@googlegroups.com. Visit this group at http://groups.google.com/group/django-developers. To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/CANJp-yhtS4xVy4MLoOs%2B0%2B_9AnkZqmpw%2BVmG8pO%3DQ%2Byda01yAA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
