id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
27996	Add pgcrypto extension  and GEN_RANDOM_UUID function to contrib.postgres	Paolo Melchiorre	Paolo Melchiorre	"After the introduction of the UUID Field in Django 1.8, I believe that django.contrib.postgres could benefit from some custom functions based on the pgcrypto extension of PostgreSQL (see https://www.postgresql.org/docs/9.6/static/pgcrypto.html). That kind of functions would be very helpful for apply a migration that adds a unique non-nullable field to a table with existing rows.

Starting from ""Migrations that add unique fields"" (see https://docs.djangoproject.com/en/dev/howto/writing-migrations/#migrations-that-add-unique-fields) I speed up the `gen_uuid` using `GEN_RANDOM_UUID` function changing it from:

{{{
import uuid

def gen_uuid(apps, schema_editor):
    MyModel = apps.get_model('myapp', 'MyModel')
    for row in MyModel.objects.all():
        row.uuid = uuid.uuid4()
        row.save(update_fields=['uuid'])
}}}

to

{{{
from django.contrib.postgres.functions import RandomUUID

def gen_uuid(apps, schema_editor):
    MyModel = apps.get_model('myapp', 'MyModel')
    MyModel.objects.update(uuid=RandomUUID())
}}}

Using this function on my system the time to migrate more than 10000 objects decreased from

{{{
real 0m15.988s
user 0m10.680s
sys 0m0.508s
}}}

to


{{{
real 0m2.957s
user 0m1.736s
sys 0m0.072s
}}}

I already implemented a solution for thi feature and I've created a [https://github.com/django/django/pull/8265 PR]"	New feature	assigned	contrib.postgres	dev	Normal		uuid extension function random postgresql cryptography		Accepted	1	0	0	0	0	0