If we come from django < 1.7 and we have some initial data, or in a particular migration step we want to run some sql code from a file to do a data migration. here’s they way:

for example if we have the following directory structure, of a django app:

- app_name/
  - sql/
    - initial_data.sql
    - migrate_data.sql
  - migrations/
    - __init__.py
    - 0001_initial.py
  - models.py
  - views.py
  - urls.py
  - __init__.py

then run:

python manage.py makemigrations --empty app_name

where app_name is the name of our application. Then we can rename the new generated file to to 0002_intial_data.py or whatever other name is good for us. If we are using django >= 1.8 we can do just this (I didn’t try it yet):

python manage.py makemigrations --name inital_data --empty app_name

now our directory structure will be like this (with a new migration file)

  
  - app_name/
    - sql/
      - initial_data.sql
      - migrate_data.sql
    - migrations/
      - __init__.py
      - 0001_initial.py
      - 0001_initial_data.py
    - models.py
    - views.py
    - urls.py
    - __init__.py

if we open our new migration file we will see something like this:

from django.db import models, migrations

class Migration(migrations.Migration):

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

    operations = [
    ]

now we have to add operations to the operations list, and we should be able to run python code. So what we need is the method RunPython from the django migrations module.

import os

from django.db import connection, migrations

def load_data_from_sql(filename):
    file_path = os.path.join(os.path.dirname(__file__), '../sql/', filename)
    sql_statement = open(file_path).read()
    with connection.cursor() as c:
        c.execute(sql_statement)

initial_data = lambda: load_data_from_sql('initial_data.sql')
migrate_data = lambda: load_data_from_sql('migrate_data.sql')


class Migration(migrations.Migration):

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

    operations = [
        migrations.RunPython(initial_data),
        migrations.RunPython(migrate_data),
    ]
  • First we create a function that given a file name, reads that file from the app’s migrations directory and execute the sql code of that file in the database.
  • then we create some “on the fly” functions or “lambda” functions for every file that we need to execute.
  • finally we add those functions to the operations list using the method RunPython.

May be you can set the funcion load_data_from_sql inside another file to re-use it in different places/migrations.

After that all we need to do is run the migrations:

python manage.py  migrate app_name

and we are done!

HOOOLA