Django 2.2 and PostgreSQL 11 about django-pg-zero-downtime-migrations HOT 6 CLOSED

Ahh you're right about the weird way Django deals with database level defaults. This is already tracked in https://code.djangoproject.com/ticket/470 which you might want to CC.

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Thanks for all your hardwork, @tbicr!

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Hi, @charettes

I'll see 3 different issues in your:

1. A bit unclear what warnings/errors you propose to integrate to Django's core, because standard postgres backend extend base backend, but for different databases this warnings can be different.

So I can help you to highlight potential unsafe operations for postgres. But I cannot to decide to add it to django core.

2. I'll look at DatabaseSchemaEditor a bit later. Will keep you updated.

3. About postgres 11 it's save to add DEFAULT value but standard django's behavior use it only to set all values in new column and than drop DEFAULT, see example:

    dependencies = [
        ('yyy', '0001_initial'),
    ]

    operations = [
        migrations.AddField(
            model_name='test',
            name='test2',
            field=models.CharField(default='test', max_length=10),
        ),
    ]

Will execute next SQL:

LOG:  statement: ALTER TABLE "yyy_test" ADD COLUMN "test2" varchar(10) DEFAULT 'test' NOT NULL
LOG:  statement: ALTER TABLE "yyy_test" ALTER COLUMN "test2" DROP DEFAULT
LOG:  statement: COMMIT

If you try to insert any new row to this table from old code (that doesn't know about new changes yet), then you will get exception that test2 column required. So unfortunately postgres 11 doesn't bring much for current django logic.

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@charettes , thanks that highlight me point with DatabaseSchemaEditor changes, I'll commented it, there are a few points that should be changed for django 2.2 support, so I will wait for django 2.2 release to fix all issues.

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Hi, @charettes , I created django/django#10789 (https://code.djangoproject.com/ticket/30060#ticket) and #6 for django 2.2 support.

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django 2.2 support added in #6

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