Opened 4 years ago

Last modified 4 years ago

#31665 closed Bug

Auto-migrations fail on postgres when Charfield's default value is longer than old constraint — at Version 3

Reported by: shadytradesman Owned by: nobody
Component: Migrations Version: 2.2
Severity: Normal Keywords: charfield resize default alterfield max_length
Cc: Triage Stage: Unreviewed
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description (last modified by shadytradesman)

Migration to create the field

# Generated by Django 2.2.12 on 2020-05-29 19:06

import cells.models
from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('cells', '0003_auto_20200529_1832'),
    ]

    operations = [
        migrations.AddField(
            model_name='cell',
            name='invite_link_secret_key',
            field=models.CharField(default=cells.models.random_string, max_length=7),
        ),
    ]

Migration to resize the field:

# Generated by Django 2.2.12 on 2020-05-29 23:56

import cells.models
from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('cells', '0004_auto_20200529_2006'),
    ]

    operations = [
        migrations.AlterField(
            model_name='cell',
            name='invite_link_secret_key',
            field=models.CharField(default=cells.models.random_string, max_length=64),
        ),
    ]

Here is the random string method:

def random_string():
    return hashlib.sha224(bytes(random.randint(1, 99999999))).hexdigest()

This migration worked on mysql when I was developing locally, but it was because I updated the random_string() function to provide a string that was longer after I ran the migration. It failed when I ran it against my prod Postgres 9.5.15 database.

I suggest including default value functions in the migrations so that when old migrations are run against new code, you don't have issues.

Change History (3)

comment:1 by shadytradesman, 4 years ago

Description: modified (diff)

comment:2 by shadytradesman, 4 years ago

Description: modified (diff)
Summary: Auto-migrations fail on postgres when resizing Charfield and setting default value longer than old constraintAuto-migrations fail on postgres when Charfield's default value is longer than old constraint

comment:3 by shadytradesman, 4 years ago

Description: modified (diff)
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