Making schema changes

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This is a page about improving or modifying OpenHatch.

We call that "Hacking OpenHatch," and there is a whole category of pages about that.


This document describes how to make database schema changes to OpenHatch in Django using South.

Making schema changes

  1. Make the schema change you want to the relevant Django model (or add a model). An example model file is mysite/profile/models.py.
  2. Use South's schema migration facilities to calculate the differences between the known schema and your updated schema. Run:
    ./manage.py schemamigration APPNAME --auto
    

    where APPNAME is the mysite app in which you've made the schema change. Example appnames are "profile", "customs", and "account", which correspond to app directories within mysite/.

    This command produces a migration file within the migration subdirectory of the app's directory, of the form 00XX_name_of_schema_change.py, where XX is the number of the migration for this app.
  3. Update the database schema by applying the contents of the migration file:
    ./manage.py migrate APPNAME
    
  4. Commit the model change and migration file.

Here's an example

  1. Make the schema change in the model file:
    --- a/mysite/profile/models.py
    +++ b/mysite/profile/models.py
    @@ -650,6 +650,7 @@ class PortfolioEntry(models.Model):
         is_archived = models.BooleanField(default=False)
         sort_order = models.IntegerField(default=0)
         use_my_description = models.BooleanField(default=True, verbose_name='')
    +    receive_maintainer_notifications = models.BooleanField(default=True)
    
  2. Generate the migration file:
    oh-mainline$ ./manage.py schemamigration profile --auto
     + Added field receive_maintainer_notifications on profile.PortfolioEntry
    Created 0088_auto__add_field_portfolioentry_receive_maintainer_notifications.py. You can now apply this migration with: ./manage.py migrate profile
    
  3. Apply the schema change:
    oh-mainline$ ./manage.py migrate profile
    Running migrations for profile:
     - Migrating forwards to 0088_add_field_portfolioentry_receive_maintainer_notifications.
     > profile:0088_add_field_portfolioentry_receive_maintainer_notifications
    2011-02-20 19:50:14,498 execute:129 DEBUG    south execute "ALTER TABLE `profile_portfolioentry` ADD COLUMN `receive_maintainer_notifications` bool NOT NULL DEFAULT True;" with params "[]"
    2011-02-20 19:50:14,499 execute:129 DEBUG    south execute "ALTER TABLE `profile_portfolioentry` ;" with params "[]"
    2011-02-20 19:50:14,500 execute:129 DEBUG    south execute "ALTER TABLE `profile_portfolioentry` ALTER COLUMN `receive_maintainer_notifications` DROP DEFAULT;" with params "[]"
    2011-02-20 19:50:14,501 execute:129 DEBUG    south execute "ALTER TABLE `profile_portfolioentry` MODIFY `receive_maintainer_notifications` bool NOT NULL;;" with params "[]"
    2011-02-20 19:50:14,502 execute:129 DEBUG    south execute "SET FOREIGN_KEY_CHECKS=1;" with params "[]"
    2011-02-20 19:50:14,504 execute:129 DEBUG    south execute "ALTER TABLE `profile_portfolioentry` ADD COLUMN `receive_maintainer_notifications` bool NOT NULL DEFAULT True;" with params "[]"
    2011-02-20 19:50:14,634 execute:129 DEBUG    south execute "ALTER TABLE `profile_portfolioentry` ;" with params "[]"
    2011-02-20 19:50:14,636 execute:129 DEBUG    south execute "ALTER TABLE `profile_portfolioentry` ALTER COLUMN `receive_maintainer_notifications` DROP DEFAULT;" with params "[]"
    2011-02-20 19:50:14,699 execute:129 DEBUG    south execute "ALTER TABLE `profile_portfolioentry` MODIFY `receive_maintainer_notifications` bool NOT NULL;;" with params "[]"
     - Loading initial data for profile.
    No fixtures found.
    
  4. Commit the changes to mysite/profile/models.py and mysite/profile/migrations/0088_auto__add_field_portfolioentry_receive_maintainer_notifications.py.