diff options
Diffstat (limited to 'docs/ref')
| -rw-r--r-- | docs/ref/migration-operations.txt | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/docs/ref/migration-operations.txt b/docs/ref/migration-operations.txt index 412d5196a6..5c4f09e08f 100644 --- a/docs/ref/migration-operations.txt +++ b/docs/ref/migration-operations.txt @@ -267,14 +267,18 @@ queries and parameters in the same way as :ref:`cursor.execute() If you want to include literal percent signs in the query, you have to double them if you are passing parameters. -The ``reverse_sql`` queries are executed when the migration is unapplied, so -you can reverse the changes done in the forwards queries:: +The ``reverse_sql`` queries are executed when the migration is unapplied. They +should undo what is done by the ``sql`` queries. For example, to undo the above +insertion with a deletion:: migrations.RunSQL( - [("INSERT INTO musician (name) VALUES (%s);", ['Reinhardt'])], - [("DELETE FROM musician where name=%s;", ['Reinhardt'])], + sql=[("INSERT INTO musician (name) VALUES (%s);", ['Reinhardt'])], + reverse_sql=[("DELETE FROM musician where name=%s;", ['Reinhardt'])], ) +If ``reverse_sql`` is ``None`` (the default), the ``RunSQL`` operation is +irreversible. + The ``state_operations`` argument is so you can supply operations that are equivalent to the SQL in terms of project state; for example, if you are manually creating a column, you should pass in a list containing an ``AddField`` @@ -321,7 +325,8 @@ instance of :class:`SchemaEditor The ``reverse_code`` argument is called when unapplying migrations. This callable should undo what is done in the ``code`` callable so that the -migration is reversible. +migration is reversible. If ``reverse_code`` is ``None`` (the default), the +``RunPython`` operation is irreversible. The optional ``hints`` argument will be passed as ``**hints`` to the :meth:`allow_migrate` method of database routers to assist them in making a |