Added a db_type() method to the database Field class. This is a hook for calculating the database column type for a given Field. Also converted all management.py CREATE TABLE statements to use db_type(), which made that code cleaner. The Field.get_internal_type() hook still exists, but we should consider removing it at some point, because db_type() is more general. Also added docs -- the beginnings of docs on how to create custom database Field classes. This is backwards-compatible.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5725 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 25 insertions, 0 deletions

diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index bc6d551a4c..5e3509857b 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -1,3 +1,4 @@
+from django.db import get_creation_module
 from django.db.models import signals
 from django.dispatch import dispatcher
 from django.conf import settings
@@ -117,6 +118,30 @@ class Field(object):
         """
         return value
 
+    def db_type(self):
+        """
+        Returns the database column data type for this field, taking into
+        account the DATABASE_ENGINE setting.
+        """
+        # The default implementation of this method looks at the
+        # backend-specific DATA_TYPES dictionary, looking up the field by its
+        # "internal type".
+        #
+        # A Field class can implement the get_internal_type() method to specify
+        # which *preexisting* Django Field class it's most similar to -- i.e.,
+        # an XMLField is represented by a TEXT column type, which is the same
+        # as the TextField Django field type, which means XMLField's
+        # get_internal_type() returns 'TextField'.
+        #
+        # But the limitation of the get_internal_type() / DATA_TYPES approach
+        # is that it cannot handle database column types that aren't already
+        # mapped to one of the built-in Django field types. In this case, you
+        # can implement db_type() instead of get_internal_type() to specify
+        # exactly which wacky database column type you want to use.
+        data_types = get_creation_module().DATA_TYPES
+        internal_type = self.get_internal_type()
+        return data_types[internal_type] % self.__dict__
+
     def validate_full(self, field_data, all_data):
         """
         Returns a list of errors for this field. This is the main interface,