#26476: Migration preserve_default does not work properly
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Reporter: madEng84 | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
Severity: Normal | Keywords: preserve_default sqlmigrate
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Hi all, I'm using Django<1.9
When i change my model adding a default to one field or adding a new field
to existing model with a default, and I launch:
`./manage.py sqlmigrate my_app_label my_migration_name`
I see:
''BEGIN;
ALTER TABLE `my_app_label` ADD COLUMN `my_char_field` varchar(36) DEFAULT
test NOT NULL;
ALTER TABLE `my_app_label` ALTER COLUMN `my_char_field` DROP DEFAULT;
COMMIT;''
Reading Docs ([https://docs.djangoproject.com/en/1.8/ref/migration-
operations/#alterfield]) i can see, about that ''preserve_default'', that
:
The preserve_default argument indicates whether the field’s default
value is permanent and should be baked into the project state (True), or
if it is temporary and just for this migration (False) - usually because
the migration is altering a nullable field to a non-nullable one and needs
a default value to put into existing rows. It does not affect the behavior
of setting defaults in the database directly - '''Django never sets
database defaults and always applies them in the Django ORM code'''.
So why I see launching sqlmigrate **DEFAULT** and than **DROP DEFAULT** ?
For large databases this could be an heavy pair of query.
Best Regards
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Ticket URL: <https://code.djangoproject.com/ticket/26476>
Django <https://code.djangoproject.com/>
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