#31646: Support annotated check constraints.
-------------------------------------+-------------------------------------
     Reporter:  Tonye Jack           |                    Owner:  nobody
         Type:  New feature          |                   Status:  closed
    Component:  Database layer       |                  Version:  2.2
  (models, ORM)                      |
     Severity:  Normal               |               Resolution:  wontfix
     Keywords:  check-constraints,   |             Triage Stage:
  model constraints                  |  Unreviewed
    Has patch:  0                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):

 * status:  new => closed
 * needs_docs:  1 => 0
 * resolution:   => wontfix
 * needs_tests:  1 => 0
 * easy:  1 => 0


Comment:

 `CheckConstraint` accepts any boolean expression since Django 3.1+ so this
 particular one can be expressed using `RawSQL`

 {{{#!python
 CheckConstraint(
     check=RawSQL(
         'non_null_count(amount::integer , amount_off::integer,
 percentage::integer) = 1',
         output_field=models.BooleanField(),
      )
 )
 }}}

 Or event `Func`, `Cast`, and `Exact`.

 {{{#!python
 non_null_count = Func(Cast('amount', models.IntegerField()),
 Cast('amount_off', models.IntegerField()), Cast('percentage',
 models.IntegerField()), function='non_null_count')
 CheckConstraint(
     check=Exact(non_null_count, 1),
 )
 }}}

-- 
Ticket URL: <https://code.djangoproject.com/ticket/31646#comment:2>
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