Wrong output when alter field in sqlmigrate.

[jinzhao]

I start a container in docker image python:2.7-slim and test like this.

1. Use django-admin startproject mysite to start a project.
2. Use ./manage.py startapp app to add a app.
3. Add a model in app/models.py.

   class Abcd(models.Model):
       name = models.CharField(max_length=100)
   

4. Edit mysite/settings.py. Add app.apps.AppConfig to INSTALLED_APPS
5. Run ./manage.py makemigrations && ./manage.py migrate.
6. Edit app/models.py. Change the max length of name field to 1000.
7. Run ./manage.py makemigrations && ./manage.py sqlmigrate app 0002.

Here is the output.

ALTER TABLE "app_abcd" RENAME TO "app_abcd__old";
CREATE TABLE "app_abcd" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "name" varchar(1000) NOT NULL);
INSERT INTO "app_abcd" ("id", "name") SELECT "id", "name" FROM "app_abcd__old";
DROP TABLE "app_abcd__old";
COMMIT;

It will create a new table, and drop all the data in the old table.

The migrate file seems correct. Here is app/migrations/0002_auto_20170319_1003.py

# -*- coding: utf-8 -*-
# Generated by Django 1.10.6 on 2017-03-19 10:03
from __future__ import unicode_literals

from django.db import migrations, models


class Migration(migrations.Migration):

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

    operations = [
        migrations.AlterField(
            model_name='abcd',
            name='name',
            field=models.CharField(max_length=1000),
        ),
    ]

Django is installed by pip, django.VERSION is (1, 10, 6, u'final', 0).

[Tim Graham]

What is the bug? Creating a new table and copy over the data is expected behavior as described in the ​SQLite migration docs.

[jinzhao]

You are right. I didn't notice the difference between sqlite and mysql. Sorry to create a wrong ticket.

Replying to Tim Graham:

What is the bug? Creating a new table and copy over the data is expected behavior as described in the ​SQLite migration docs.