Kered.org/Blog » Blog Archive » Django Schema Evolution

Django Schema Evolution

I’ve ported my schema evolution work from my SoC project last summer to Django v0.96. To use it, download the patch below, and run the following:

$ cd /<path_to_python_dir>/site-packages/django/
$ patch -p1 < ~/<download_dir>/django_schema_evolution-v096patch.txt

It should output the following:

patching file core/management.py
patching file db/backends/mysql/base.py
patching file db/backends/mysql/introspection.py
patching file db/backends/postgresql/base.py
patching file db/backends/postgresql/introspection.py
patching file db/backends/sqlite3/base.py
patching file db/backends/sqlite3/introspection.py
patching file db/models/fields/__init__.py
patching file db/models/options.py

To use it:

$ cd /<path_to_project_dir>/
$ ./manage.py sqlevolve <app_name>

It should output something like this:

BEGIN;
ALTER TABLE `main_query` CHANGE COLUMN `accuracy` `accuracynew` numeric(10, 6) NULL;
ALTER TABLE `main_query` ADD COLUMN `price` varchar(256) NULL;
COMMIT;

Assuming you have a model such as this:

class Query(models.Model):
    query = models.CharField(maxlength=256, blank=False)
    accuracynew = models.FloatField(max_digits=10, decimal_places=6, null=True, blank=True, aka='accuracy')
    price = models.CharField(maxlength=256, null=True, blank=True) # new column

Note the aka field where I changed the name of “accuracy” to “accuracynew”.

Source code:

django_schema_evolution-v096patch.txt

Documentation:

http://code.djangoproject.com/wiki/SchemaEvolutionDocumentation

Let me know if you find any bugs.

UPDATE: This project is now on Google Code: http://code.google.com/p/deseb/

This entry was posted on Thursday, July 19th, 2007 at 4:42 pm and is filed under django, google / SoC, open source, programming. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

15 Responses to “Django Schema Evolution”

Jökull Says:
July 20th, 2007 at 11:05 am
This looks very promising. How does this compare to Rails’ Migration feature? Looks a lot smoother.
Harish Mallipeddi Says:
July 23rd, 2007 at 1:12 am
How to run custom SQL as part of a schema migration? For instance if I wanted to combine two columns into one column?
David Grant Says:
July 23rd, 2007 at 2:32 pm
Is this going to be merged into Django proper?
rtconner Says:
July 24th, 2007 at 6:51 pm
Or is there any equavalent for this planned for Django root? does this patch work with .97-latest?
derek Says:
July 24th, 2007 at 10:40 pm
david: that’s my goal
rtconner: yes to your second question
buriy Says:
July 28th, 2007 at 3:34 am
Don’t work for postgres_psycopg2 backend! If you copy changes from postgres backend, don’t work also.
File “D:\web\projects\ef\manage.py”, line 11, in ?
execute_manager(settings)
File “d:\program\python24\lib\site-packages\django\core\management.py”, line 1952, in execute_manager
execute_from_command_line(action_mapping, argv)
File “d:\program\python24\lib\site-packages\django\core\management.py”, line 1843, in execute_from_command_line
action_mapping[action](int(options.verbosity), options.interactive)
File “d:\program\python24\lib\site-packages\django\core\management.py”, line 793, in syncdb
for sql in get_sql_evolution(app):
File “d:\program\python24\lib\site-packages\django\core\management.py”, line 546, in get_sql_evolution
output = get_sql_evolution_check_for_dead_fields(klass, new_table_name)
File “d:\program\python24\lib\site-packages\django\core\management.py”, line 698, in get_sql_evolution_check_for_dead_fields
suspect_fields.difference_update(f.aka)
TypeError: iteration over non-sequence
derek Says:
July 30th, 2007 at 1:12 pm
buriy: fixed this in the schema-evolution branch. (i assume this is where you ran across it, not in the v0.96 patch, right?)
Mike Heald Says:
July 31st, 2007 at 5:08 am
Looks like excellent stuff! Looking closer at what you’re doing here, it looks like our migration projects would actually work very nicely together! A situation where individual developers in a team could use evolution to generate the migrations they need, review them, and then use dbmigration to automatically roll them out to demo/UAT/live servers would be my ideal way of doing things.
derek Says:
July 31st, 2007 at 2:04 pm
mike, i couldn’t agree more.
buriy Says:
August 6th, 2007 at 5:50 am
Please, patch for django-trunk.
By the way, works perfectly for django-newforms admin!
Zarek Says:
August 15th, 2007 at 7:48 am
This code is very interesting for creating an audit trail for a given model.

http://code.djangoproject.com/wiki/AuditTrail
» Actualización de Estado de Django: 22 de Julio - Blog de Marcelo Ramos Says:
December 16th, 2007 at 10:45 pm
[...] Aparentemente pisándole los talones al proyecto de Mike, Derek Anderson, el autor del proyecto schema-evolution del Summer of Code 2006, ha actualizado su código para que funcione adecuadamente con la versión 0.96 de Django. Derek afirma que el schema-evolution también debería funcionar correctamente con la versión trunk de Django . [...]
krl Says:
May 15th, 2008 at 12:03 am
I don’t know if you are interested guys but there is an interesting new approach to schema evolution, is called PRISM, developed at UCLA is a tool to support schema evolution in relational DB.

there is a video of th interface here: http://yellowstone.cs.ucla.edu/schema-evolution/documents/Prism-Demo.mov

while from here: http://yellowstone.cs.ucla.edu/schema-evolution/index.php/PrismDemo you can access the on-line demo.
SQL Tutorials Says:
April 30th, 2009 at 10:11 pm
You know, the thing about SQL is, that there is virtually nothing that can replace it.

Does anyone know if a substitute exists for sql? I mean besides MS SQL and Oracle and all that jazz. Thanks.
Carroll B. Merriman Says:
March 6th, 2010 at 1:47 pm
Thanks for your article. I am new at django and this will be a big help.

Django Schema Evolution

15 Responses to “Django Schema Evolution”

Leave a Reply