Re: Data migration using RunPython

Hello,

In Django, you can instanciate objects from your model without
persist it to the database. The way you do it is Country(name=..., ...).

In order to create multiple objects at once, you can
call the bulk_create method on the manager with a list
of object to persist.

The using(db_alias) is instanciating the manager.
I won't explain further cause my knowledge of this area
is reduced.

Have a good one

On 03/05/2015 01:20 AM, Murthy Sandeep wrote:
> I am working on a data migration for my Django app to populate
> the main table in the db with data that will form the mainstay of
> the app - this is persistent/permanent data that may added to but
> never deleted.
>
> My reference is the Django 1.7 documentation and in particular an
> example on page
>
> https://docs.djangoproject.com/en/1.7/ref/migration-operations/#django.db.migrations.operations.RunPython
>
> with a custom method called forward_funcs:
>
> def forwards_func(apps, schema_editor):
>
> # We get the model from the versioned app registry;
> # if we directly import it, it'll be the wrong version
>
>
> Country = apps.get_model("myapp", "Country")
> db_alias = schema_editor.connection.alias
> Country.objects.using(db_alias).bulk_create([
> Country(name="USA", code="us"),
> Country(name="France", code="fr"),])
>
> I was wondering if someone could please explain what is happening
> here and how this method works - is the argument to bulk_create a
> list of namedtuple objects called Country or are these Country model
> objects?
>
> Also could someone please explain what db_alias is?
>
> Sandeep
>
>

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