Django: What are the best practices to migrate a project from sqlite to PostgreSQL

Question

I need to migrate a complex project from sqlite to PostgreSQL. A lot of people seems to have problem with foreign keys, data truncature and so on...

• Is there a full automated utility ?
• Do I need to check some data or schema before the migration ?

Edit : I tried django-command-extensions DumpScript but it doesn't run on my 2GB RAM PC with my current DataSet.

Answer 1

In my experience, dumping & restoring from SQL doesn't work properly.

You should follow this sequence instead:

1. Dump db contents to json

$ ./manage.py dumpdata > dump.json 

2. Switch the backend in settings.py

DATABASES = {     # COMMENT OUT:     # 'default': dj_database_url.config(default='sqlite:////full/path/to/your/database/file.sqlite'),     # ADD THIS INSTEAD:     'default': dj_database_url.config(default='postgres://localhost:5432/postgres_db_name'), } 

3. Syncdb and migrate the new DB to the same table structure

$ ./manage.py syncdb $ ./manage.py migrate 

4. Load the json to the new db.

$ ./manage.py loaddata dump.json 

5. Congrats! Now the new data is in your postgres db.

Answer 2

The following is a refinement of Nimo's answer and Stephen's answer for Django 1.7+:

1. ./manage.py dumpdata --natural-primary --natural-foreign > dump.json
2. Change DATABASES in settings.py to point to the new (PostgreSQL) db.
3. ./manage.py migrate
4. ./manage.py loaddata dump.json

One problem I encountered is that SQLite doesn't seem to actually enforce the maximum length for CharFields. In my case, this made the loaddata step fail. I was able to find (and delete) model instances with too long CharField values via:

MyModel.objects.extra(where=["LENGTH(text) > 20"]).delete() 

Once I did this before step 1. above, everything worked.