#21454: Ignoring certain fields on INSERT and UPDATE queries
-------------------------------------+-------------------------------------
Reporter: mpessas | Owner: mpessas
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: oracle | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
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Comment (by owais):
== Update ==
Moved the delegation logic from models closer to the code that generates
the queries. This makes the implementation a bit more robust as most
higher level APIs should just work without the need to update anything. It
also allowed me to add support to querysets for delegation.
== Field Options ==
=== `delegated=True|False` ===
A shortcut that automatically sets the the following option to True when
no value is provided for them.
=== `delegated_on_insert=True|False` ===
If True, the value of this field will not be skipped from the `INSERT`
statement completely. This automatically sets `return_on_insert` to `True`
if not value is given. Supported on all backends.
=== `delegated_on_update=True|False` ===
If True, the value of this field will not be skipped from the `UPDATE`
statement completely. This automatically sets `return_on_update` to `True`
if not value is given. Supported on all backends.
=== `return_on_insert=True|False` ===
If True, the value for field is loaded and assigned from the database
along with the `INSERT` statement. Supported on PostgreSQL using the
`RETURNING` clause and Oracle using the `RETURNING INTO` clause.
=== `return_on_update=True|False` ===
If True, the value for field is loaded and assigned from the database
along with the `UPDATE` statement. Supported on PostgreSQL using the
`RETURNING` clause and Oracle using the `RETURNING INTO` clause.
== Model API Changes ==
`save()` method now takes an optional argument called `ignore_delegated`
which can be a list of delegated field names. This negates the behavior of
`delegated_on_insert` and `delegated_on_update`.
== Queryset/Manager API Changes ==
Querysets have a new method call `ignore_delegated` which takes names of
delegated fields as arguments and negates the behavior of
`delegated_on_insert` and `delegated_on_update` for any subsequent
operations. For example, if we have a delegated field called `created_at`
on a model, we can temporarily disable delegation to DB for a single
query.
{{{
class MyModel(models.Model):
pytthon_ts = fields.DatetimeField()
db_ts = fields.DatetimeField(delegated=True)
# This will only update python_ts as `db_ts` is delegated to database
MyModel.objects.update(db_ts=now(), python_ts=now())
# However, this will update both
MyModel.objects.ignore_delegated('db_ts').update(db_ts=now(),
python_on=now())
}}}
The above example also applies to `Model.objects.create()`.
--
Ticket URL: <https://code.djangoproject.com/ticket/21454#comment:21>
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