Re: [Django] #32811: Annotate removes Meta.ordering

[Django]

#32811: Annotate removes Meta.ordering
-+-
 Reporter:  pirelle  |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  3.2
  (models, ORM)  |
 Severity:  Release blocker  |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-

Comment (by Mariusz Felisiak):

 Replying to [comment:2 Peter Law]:
 > Request that this be reconsidered.
 >
 > ...
 > At the very least I think this (current behaviour) needs to be clearly
 documented as a part of both the `Meta.ordering` and aggregation docs,
 however to be honest I would prefer the previous behaviour. It feels very
 surprising that Django will silently drop part of its model configuration
 in some cases!
 > At least if this were documented people could see what those cases were,
 however at the moment the only way to know is when you're bitten by the
 issue described here.

 The previous behavior was implicit, unexpected, and caused many support
 questions. We reached the consensus that removing any default ordering for
 grouped queries is the right thing to do. You can always add `order_by()`
 (as [https://docs.djangoproject.com/en/3.2/topics/db/aggregation
 /#interaction-with-order-by documented]).

 You can start a discussion on DevelopersMailingList if you don't agree,
 but I don't think there would be consensus to restore it. Personally, I'm
 strongly against it.

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Re: [Django] #32811: Annotate removes Meta.ordering

[Django]

#32811: Annotate removes Meta.ordering
-+-
 Reporter:  pirelle  |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  3.2
  (models, ORM)  |
 Severity:  Release blocker  |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-

Comment (by Peter Law):

 Request that this be reconsidered.

 My use-case was similar to the one mentioned here, however I was loading
 full models (with a similar count annotation) and not any form of
 `.values()`. Given the history it seems likely that that was never the
 intention.

 I can see that this was previously deprecated and may now be expected,
 however it does not appear to be documented anywhere and is very
 surprising.

 Here's where I've (since) checked for docs relating to this:
 - https://docs.djangoproject.com/en/3.2/ref/models/options/#ordering
 - https://docs.djangoproject.com/en/3.2/topics/db/aggregation/
 - https://docs.djangoproject.com/en/3.2/ref/models/expressions/#aggregate-
 expressions

 What I've seen of the reasoning for the deprecation appears to be related
 specifically to `.values()` queries, and then really to cases where that
 is used to create a grouping ''of the main queried table'' (where the user
 is probably aware that that's what they're doing). However the behaviour
 change impacts ''all'' querysets (including those which return full
 models) and the behaviour here is ''not'' intending to create a grouping
 of things on the main table, but rather of a related table for the
 purposes of counting (where the user is unlikely to be aware that a group-
 by is the result).

 Perhaps the core issue here is that the ORM doesn't have an explicit
 "group by" mechanism and so is having to infer this by pattern matching
 the structure of the `QuerySet`, leading to the issues like the original
 one where default ordering is applied in ways that produce potentially
 unexpected results.

 At the very least I think this (current behaviour) needs to be clearly
 documented as a part of both the `Meta.ordering` and aggregation docs,
 however to be honest I would prefer the previous behaviour. It feels very
 surprising that Django will silently drop part of its model configuration
 in some cases!
 At least if this were documented people could see what those cases were,
 however at the moment the only way to know is when you're bitten by the
 issue described here.

 Aside: the original ticket (https://code.djangoproject.com/ticket/10574)
 appears to suggest that part of the motivation is that in queries such as
 `Model.objects.values('data')` applying the default ordering is redundant,
 which I'd strongly argue against -- having values-only results ordered by
 something (even a field not loaded) seems entirely useful to me.

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Ticket URL: 
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Re: [Django] #32811: Annotate removes Meta.ordering

[Django]

#32811: Annotate removes Meta.ordering
-+-
 Reporter:  pirelle  |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  3.2
  (models, ORM)  |
 Severity:  Release blocker  |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by Mariusz Felisiak):

 * status:  new => closed
 * resolution:   => invalid
 * easy:  1 => 0


Comment:

 This is an expected behavior. `Meta.ordering` doesn't affect `GROUP BY`
 queries after 0ddb4ebf7bfcc4730c80a772dd146a49ef6895f6 (which was
 deprecated in 1b1f64ee5a78cc217fead52cbae23114502cf564).

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Ticket URL: 
Django 
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[Django] #32811: Annotate removes Meta.ordering

[Django]

#32811: Annotate removes Meta.ordering
-+-
   Reporter:  pirelle|  Owner:  nobody
   Type:  Bug| Status:  new
  Component:  Database   |Version:  3.2
  layer (models, ORM)|
   Severity:  Release|   Keywords:
  blocker|
   Triage Stage: |  Has patch:  0
  Unreviewed |
Needs documentation:  0  |Needs tests:  0
Patch needs improvement:  0  |  Easy pickings:  1
  UI/UX:  0  |
-+-
 This is very simplified example

 {{{
 In [5]: str(Order.objects.values("id", "ordered_at").all().query)
 Out[5]: 'SELECT "orders_order"."id", "orders_order"."ordered_at" FROM
 "orders_order" ORDER BY "orders_order"."ordered_at" DESC'

 In [6]: str(Order.objects.values("id",
 "ordered_at").annotate(c=Count("id")).all().query)
 Out[6]: 'SELECT "orders_order"."id", "orders_order"."ordered_at",
 COUNT("orders_order"."id") AS "c" FROM "orders_order" GROUP BY
 "orders_order"."id"'
 }}}
 As you can see ORDER BY disappears when annotate with Count exists.
 It used to work on 3.0, but stopped working in 3.1 and 3.2

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