Turns out there was a tiny class Meta at the very bottom of the very big
model, obfuscating mine defining the index.. Something not even ChatGPT
could imagine!
On Thursday, December 5, 2024 at 12:31:01 PM UTC+1 RANGA BHARATH JINKA
wrote:
> Hi,
>
> The issue is that partial indexes with conditions (condition attribute in
> models.Index) were introduced in *Django 3.2*, but they rely on the
> database backend's ability to support them. PostgreSQL does support partial
> indexes, so that part should be fine. However, your problem likely stems
> from the following points:
> 1. *Condition on channel_type Value*
>
> The condition models.Q(channel_type="42") is valid in Python, but
> PostgreSQL requires conditions to work with literal values that match the
> column type. If channel_type is a CharField, "42" is fine. However,
> ensure that the value and type match your database schema.
>
> - Example: If channel_type is actually an integer-like value stored in
> a CharField, ensure "42" matches the expected format.
>
> ------------------------------
> 2. *Potential Issue with Makemigrations*
>
> Even if the code is correct, makemigrations might not detect the change
> in the Meta class because migrations only track model-level changes. If
> makemigrations doesn’t pick up the index:
>
> -
>
> *Manually Generate the Migration:* Use makemigrations with the --empty
> flag and define the index manually.
>
> python manage.py makemigrations --empty your_app_name
>
> Then, in the generated migration file, define the index:
>
> from django.db import migrations, models
> import django.db.models.expressions
>
> class Migration(migrations.Migration):
> dependencies = [
> ('your_app_name', 'previous_migration'),
> ]
>
> operations = [
> migrations.AddIndex(
> model_name='episode',
> index=models.Index(
> name='ch_last_seen_date',
> fields=['last_seen_date'],
> condition=models.Q(channel_type='42'),
> ),
> ),
> ]
>
>
> ------------------------------
> 3. *Check Your Environment*
>
> Ensure your Django project environment is up-to-date and consistent:
>
> - Confirm your django.db.backends.postgresql version supports the
> feature.
> - Run python manage.py showmigrations to ensure your migrations are
> applied.
>
> ------------------------------
> Debugging Steps
>
> 1.
>
> Double-check the condition syntax:
>
> condition=models.Q(channel_type='42')
>
> Ensure channel_type and '42' match your schema's type expectations.
> 2.
>
> Confirm makemigrations is running in the correct app and picking up
> changes:
>
> python manage.py makemigrations your_app_name
>
> 3.
>
> Review your migration file for errors or omissions.
>
> If the issue persists after these steps, consider upgrading to the latest
> Django version for potential bug fixes in migration handling.
>
> On Thu, Dec 5, 2024 at 4:11 PM mccc <mcic...@gmail.com> wrote:
>
>> Hello,
>>
>> We want to have a partial index (db backend is Postgres) on a
>> datetimefield, so we added this code to the Meta class:
>>
>> class Episode(models.Model):
>> channel_type = models.CharField(max_length=16, choices=CHANNEL_TYPES)
>> last_seen_date = models.DateTimeField(auto_now_add=True)
>> class Meta:
>> indexes = [
>> models.Index(
>> name="ch_last_seen_date",
>> fields=["last_seen_date"],
>> condition=models.Q(channel_type="42"),
>> ),
>> ]
>>
>> The problem is that makemigrations doesn't seem to recognize it.
>> What could be the problem? We're on Django 3.2, which I know is old but
>> as per the documentation this should be fine..
>>
>> Thanks
>>
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>> .
>>
>
>
> --
> Thanks and Regards
>
> J. Ranga Bharath
> cell: 9110334114
>
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