Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  closed
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:  fixed
  (models, ORM)  | Triage Stage:  Ready for
 Severity:  Normal   |  checkin
 Keywords:   |  Needs documentation:  0
Has patch:  1|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by Anssi Kääriäinen ):

 In [changeset:"dad7eec6e1c1770f5d81d5c5ed2de296c1eca969"]:
 {{{
 #!CommitTicketReference repository=""
 revision="dad7eec6e1c1770f5d81d5c5ed2de296c1eca969"
 Corrected links to only()/defer() in Model documentation

 Refs #18306
 }}}

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  closed
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:  fixed
  (models, ORM)  | Triage Stage:  Ready for
 Severity:  Normal   |  checkin
 Keywords:   |  Needs documentation:  0
Has patch:  1|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by Anssi Kääriäinen ):

 * status:  reopened => closed
 * resolution:   => fixed


Comment:

 In [99321e30cebbffeafc6ae19f4f92a0a665cbf19b]:
 {{{
 #!CommitTicketReference repository=""
 revision="99321e30cebbffeafc6ae19f4f92a0a665cbf19b"
 Fixed #18306 -- Made deferred models issue update_fields on save

 Deferred models now automatically update only the fields which are
 loaded from the db (with .only() or .defer()). In addition, any field
 set manually after the load is updated on save.
 }}}

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  reopened
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Ready for
 Severity:  Normal   |  checkin
 Keywords:   |  Needs documentation:  0
Has patch:  1|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by niwi):

 Interesting! did not have in mind such cases.

 Of course, the current implementation is better and takes a lot of
 duplication of code.


 Thanks! ;)

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  reopened
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Ready for
 Severity:  Normal   |  checkin
 Keywords:   |  Needs documentation:  0
Has patch:  1|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by akaariai):

 The problem I faced was that there were multiple places in models/query.py
 where the deferred_fields would need to be calculated. The original
 implementation didn't take into account select_related (where
 get_cached_row() can return deferred instances), and qs.raw(). These just
 work with the current implementation. In addition, there is no additional
 state bookkeeping which is always a bonus. One less place for bugs to hide
 :)

 If one wants to do dirty field state tracking, the solution is to use the
 model instance itself or it's state to keep the dirty field info, and then
 just overrider the .save() method and use update_fields in there for the
 dirty fields.

 BTW I have been wondering if we should allow 'pk' in the update_fields. If
 you say `"update_fields=['pk']"`, then the primary key will be updated as
 part of the query. I know there is no cascade support in Django, but one
 can always use custom db schemas and ON UPDATE CASCADE. Seems useful to
 me. But of course not this ticket's problem...

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  reopened
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Ready for
 Severity:  Normal   |  checkin
 Keywords:   |  Needs documentation:  0
Has patch:  1|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-

Comment (by niwi):

 I liked more the solution keeping not diferred fields on models
 ``_state``, but also I like this solution.

 Great work!

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  reopened
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Ready for
 Severity:  Normal   |  checkin
 Keywords:   |  Needs documentation:  0
Has patch:  1|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by akaariai):

 * needs_better_patch:  1 => 0
 * stage:  Accepted => Ready for checkin


Comment:

 I have reviewed and polished the patch written by niwi. I created
 [https://github.com/django/django/pull/213 a pull request] as I think the
 feature is now ready for commit. Please review, or at least do a cursory
 glance for obvious mistakes.

 I wonder if I should squash the two commits into one...

 I ended up getting rid of the model._state.deferred_fields and instead
 using the instance's and class' dict to check the deferred state of the
 object when saving. The idea of using ._state was mine (or at least
 encouraged by me), sorry for pushing the wrong solution.

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  reopened
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-
Changes (by claudep):

 * status:  closed => reopened
 * resolution:  fixed =>


Comment:

 Sorry, wrong ticket number in commit message.

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  closed
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:  fixed
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-
Changes (by Claude Paroz ):

 * status:  new => closed
 * resolution:   => fixed


Comment:

 In [4f53e77f0720bd4d74b1b08857db8f7d32c65008]:
 {{{
 #!CommitTicketReference repository=""
 revision="4f53e77f0720bd4d74b1b08857db8f7d32c65008"
 Fixed #18306 -- Removed most of GeoDjango-specific deployment docs
 }}}

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by niwi):

 ;)

 I've been debugging the code, and I found the solution at 3 queries. To
 test, apply first patch #18362, so that the code is consistent.

 When you have time for this, review the code! Do not worry about time!

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by akaariai):

 One query seems like the correct result. I guess for some reason the
 profile_id isn't seen as a deferred field by the code. Unfortunately I do
 not have time to look into this more just now.

 Thanks for all your work on this!

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by niwi):

 Good work on "Cleaned up deferred model implementation", this fixes a lot
 of number of queries. But continued to have a strange case:

 {{{
 #!sql
 UPDATE "update_only_fields_person" SET "name" = Linda WHERE
 "update_only_fields_person"."id" = 1 ; args=('Linda', 1)
 SELECT "update_only_fields_employee"."person_ptr_id",
 "update_only_fields_employee"."profile_id" FROM
 "update_only_fields_employee" INNER JOIN "update_only_fields_person" ON
 ("update_only_fields_employee"."person_ptr_id" =
 "update_only_fields_person"."id") WHERE
 "update_only_fields_employee"."person_ptr_id" = 1 ; args=(1,)
 UPDATE "update_only_fields_employee" SET "profile_id" = 1 WHERE
 "update_only_fields_employee"."person_ptr_id" = 1 ; args=(1, 1)
 }}}

 With test code:

 {{{
 #!python
 def test_update_fields_inheritance_defer(self):
 profile_boss = Profile.objects.create(name='Boss', salary=3000)
 e1 = Employee.objects.create(name='Sara', gender='F',
 employee_num=1, profile=profile_boss)
 e1 = Employee.objects.only('name').get(pk=e1.pk)
 e1.name = 'Linda'
 with self.assertNumQueries(3):
 e1.save()
 }}}

 In my opinion, this case should only run a single query. I will modify the
 test for 3 queryes expect, but I'm waiting for you comment me here.

 Current Status:

 * #18362 now has attached patch
 * #17485 the solucion proposed seems rasonable (I update the patch for
 latest version)
 * ~~#18343~~ now fixed and commited to master (great work)

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by akaariai):

 I did a little digging for the reasons of the test failure. The reason is
 that the .defer/.only code stores field.attname in the skip list, but the
 update_fields checks for field.name. So, the save code sees 'profile' as a
 loaded field even if it isn't one, and tries to save it which results in
 extra queries. There is also one extra query caused by missing the code
 from pull/80.

 There are two problems here - first is that using both field.attname and
 field.name must work in update_only_fields argument. I don't believe this
 works correctly currently, at least it isn't tested. This means that both
 'profile_id', and 'profile' in update_fields argument must work. This
 should be handled in separate ticket.

 The other problem is that the .defer/.only logic in models/query.py
 doesn't use consitently the field.attname (or the field.name) when
 creating the deferred model instance. This must be fixed again in another
 ticket before fixing this ticket.

 So, at this point we have already 3 must fix before tickets. The pull/80
 issue is IMHO ready. There is a ticket for the defer/only logic for
 field.attname (#17485). I created a ticket for the ability to use
 field.attname in update_fields (ticket #18362).

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by niwi):

 Thank you very much, I will try your changes.

 Your review the patch when you have time,  there is still enough time for
 1.5

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by akaariai):

 Could you check the queries with https://github.com/django/django/pull/80
 - it contains some changes which should reduce the need for queries in
 inheritance cases, and IIRC the tests I added relied on this.

 One way to check this is to create a new branch from your local
 development branch of this feature ("git checkout -b test_with_pull_80"
 when in the local dev branch), then do "curl
 https://github.com/django/django/pull/80.patch |git am" and run the tests
 again.

 Don't update your pull request or your local development branch directly
 with the pull-80 stuff, it should be handled separately.

 I don't have time to look into the patch in detail just now.

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-
Changes (by niwi):

 * cc: niwi@… (added)


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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by niwi):

 You're absolutely right! The state can not be save on _meta attribute!

 I use the first aproach (store deferred fields on
 `modelinstance._state.deferred_fields`), because the second aproache not
 works correctlly. `self.__class__.__dict__` always contains
 `DeferredAttribute`, has been modified the field value or not.

 With my changes and your changes merged, fails two tests with unexpected
 number of queries:

 {{{
 ==
 FAIL: test_update_fields_fk_defer
 (modeltests.update_only_fields.tests.UpdateOnlyFieldsTests)
 --
 Traceback (most recent call last):
   File "/home/niwi/django/tests/modeltests/update_only_fields/tests.py",
 line 101, in test_update_fields_fk_defer
 e1.save()
   File "../django/test/testcases.py", line 273, in __exit__
 executed, self.num
 AssertionError: 2 queries executed, 1 expected
 }}}


 Generated queries:
 {{{
 (0.000) SELECT "update_only_fields_person"."id",
 "update_only_fields_employee"."person_ptr_id" FROM
 "update_only_fields_employee" INNER JOIN "update_only_fields_person" ON
 ("update_only_fields_employee"."person_ptr_id" =
 "update_only_fields_person"."id") WHERE
 "update_only_fields_employee"."person_ptr_id" = 1 ; args=(1,)
 (0.000) UPDATE "update_only_fields_employee" SET "profile_id" = 2 WHERE
 "update_only_fields_employee"."person_ptr_id" IN (SELECT
 U0."person_ptr_id" FROM "update_only_fields_employee" U0 WHERE
 U0."person_ptr_id" = 1 ); args=(2, 1)
 }}}


 {{{
 ==
 FAIL: test_update_fields_inheritance_defer
 (modeltests.update_only_fields.tests.UpdateOnlyFieldsTests)
 --
 Traceback (most recent call last):
   File "/home/niwi/django/tests/modeltests/update_only_fields/tests.py",
 line 89, in test_update_fields_inheritance_defer
 e1.save()
   File "../django/test/testcases.py", line 273, in __exit__
 executed, self.num
 AssertionError: 4 queries executed, 1 expected

 --
 }}}

 Generated queries:

 {{{
 (0.000) SELECT "update_only_fields_person"."id",
 "update_only_fields_employee"."person_ptr_id" FROM
 "update_only_fields_employee" INNER JOIN "update_only_fields_person" ON
 ("update_only_fields_employee"."person_ptr_id" =
 "update_only_fields_person"."id") WHERE
 "update_only_fields_employee"."person_ptr_id" = 1 ; args=(1,)
 (0.000) UPDATE "update_only_fields_person" SET "name" = Linda WHERE
 "update_only_fields_person"."id" = 1 ; args=('Linda', 1)
 (0.000) SELECT "update_only_fields_employee"."person_ptr_id",
 "update_only_fields_employee"."profile_id" FROM
 "update_only_fields_employee" INNER JOIN "update_only_fields_person" ON
 ("update_only_fields_employee"."person_ptr_id" =
 "update_only_fields_person"."id") WHERE
 "update_only_fields_employee"."person_ptr_id" = 1 ; args=(1,)
 (0.000) UPDATE "update_only_fields_employee" SET "profile_id" = 1 WHERE
 "update_only_fields_employee"."person_ptr_id" IN (SELECT
 U0."person_ptr_id" FROM "update_only_fields_employee" U0 WHERE
 U0."person_ptr_id" = 1 ); args=(1, 1)
 }}}


 I'm not sure it's appropriate behavior. But not for sure what would be
 appropriate.
 All changes are in the branch mentioned in my first comment.

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-
Changes (by akaariai):

 * needs_better_patch:  0 => 1


Comment:

 I spotted two issues:
   1. When doing a deferred model .save() with using argument, where the
 using is to other database than where the object was fetched, the
 "update_fields" machinery should not be used. This is a minor corner case,
 but should still work.
   2. The "deferred fields" is remembered in instance._meta, and it is
 altered when a field is set to a value - this results in changing the
 "deferred fields" property for _all_ instances, not just for the instance
 which was changed. This is a blocker issue.

 I see two ways forward:
   - remember the loaded fields (instead of deferred fields) in
 instance._state instead of instance._meta.
   - do not remember the deferred fields at all. Instead check just for
 instance._deferred. If set, then go through all fields and check if any of
 the fields are instances of !DeferredAttribute. Those fields which are
 instances of !DeferredAttribute are the deferred fields.

 The second approach should be very robust, and I think it should be used.
 The check to use is:
 {{{
 for field in self._meta.fields:
 if isinstance(self.__class__.__dict__.get(field.attname),
 DeferredAttribute):
 # add to deferred fields.
 }}}

 See: https://github.com/akaariai/django/tree/ticket_18306 for details.
 There are also some other added tests.

 I stumbled upon other issues while working on this ticket, see
 https://github.com/akaariai/django/tree/defer_inheritance_pk, #18343. Some
 (well at least one) of the added tests need this work to pass.

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  akaariai
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  0
 Keywords:   |  Patch needs improvement:  0
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-
Changes (by akaariai):

 * status:  assigned => new
 * needs_docs:  1 => 0
 * owner:  niwi => akaariai
 * needs_better_patch:  1 => 0


Comment:

 Looks excellent. I will try to find time to work this into core in the
 next couple of days.

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  niwi
 Type:   |   Status:  assigned
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  1
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by niwi):

 Now sended pull request: https://github.com/django/django/pull/65

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  niwi
 Type:   |   Status:  assigned
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  1
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-
Changes (by niwi):

 * owner:  nobody => niwi
 * status:  new => assigned


Comment:

 I've been testing, and all cases you mention, and work fine. In a few days
 I will work on the documentation and other aspects that you mentioned in
 the issue.

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  nobody
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  1
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-

Comment (by anonymous):

 I understand! I will try to implement and integrate, and if integrated
 well, great for everyone! And if not, then leave it as is.

 I have not written any kind of documentation, because I'm still doing
 tests and I'm playing a bit. When ready, do a pull-request and review the
 patch!

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  nobody
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:  Accepted
 Severity:  Normal   |  Needs documentation:  1
 Keywords:   |  Patch needs improvement:  1
Has patch:  1|UI/UX:  0
  Needs tests:  0|
Easy pickings:  0|
-+-
Changes (by akaariai):

 * needs_better_patch:  0 => 1
 * has_patch:  0 => 1
 * needs_docs:  0 => 1
 * stage:  Unreviewed => Accepted


Comment:

 The implementation looks suspiciously clean... :) However there is going
 to be some problems to get the updating of manually set fields to work
 correctly. (the a.age = 31 case in original description). Apart of this
 problem the patch needs some documentation (only()/defer() docs need a
 mention of this, maybe also in .save()).

 If it turns out to be at all problematic to support the
 model._state.update_fields attribute lets just leave that out from this
 ticket. I'd like to try that idea out, but there is no need to complicate
 this ticket with that idea.

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Re: [Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
-+-
 Reporter:  akaariai |Owner:  nobody
 Type:   |   Status:  new
  Cleanup/optimization   |  Version:  master
Component:  Database layer   |   Resolution:
  (models, ORM)  | Triage Stage:
 Severity:  Normal   |  Unreviewed
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by anonymous):

 * needs_better_patch:   => 0
 * needs_tests:   => 0
 * needs_docs:   => 0


Comment:

 The current work is done on this branch:
 https://github.com/niwibe/django/commits/defer_only_interaction

 So far I have not sent the request to pull.

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[Django] #18306: Deferred models should automatically issue update_fields when saving

[Django]

#18306: Deferred models should automatically issue update_fields when saving
--+
 Reporter:  akaariai  |  Owner:  nobody
 Type:  Cleanup/optimization  | Status:  new
Component:  Database layer (models, ORM)  |Version:  master
 Severity:  Normal|   Keywords:
 Triage Stage:  Unreviewed|  Has patch:  0
Easy pickings:  0 |  UI/UX:  0
--+
 When saving a model fetched through deferred model loading (.only() or
 .defer()) and then saving these models it would be useful to issue an
 update_fields automatically.

 Currently, all the model's deferred fields are fetched from the DB and
 then saved back - this doesn't make sense. Instead, doing
 {{{
 (assume Author with fields age + name)
 a = Author.objects.only('name').get(pk=1)
 a.name = 'Anssi'
 a.save()
 }}}
 should be equivalent to doing:
 {{{
 a = Author.objects.only('name').get(pk=1)
 a.name = 'Anssi'
 a.save(update_fields=['name'])
 }}}

 In addition, the following must work:
 {{{
 a = Author.objects.only('name').get(pk=1)
 a.name = 'Anssi'
 a.age = 31
 a.save()
 }}}
 both age and name must be saved in this case.

 Also, if save is given update_fields argument, it must override the
 deferred model argument.

 I would like to investigate the possibility of storing the fields to
 update in model._state.update_fields - the reason is that this would be a
 nice hook for 3rd party model subclasses which could use that variable to
 implement automatic tracking of changed fields. There is a lot of
 discussion of this feature in #4102, and the decision there seems clear:
 we can't include automatic change tracking in Django core. However,
 allowing easy creation of state-tracking subclasses would be a nice
 addition.

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