add populate_default kwarg to column.create, fixes issue #50

docs/changelog.rst

@@ -1,6 +1,7 @@
 0.5.5
 -----
 
+- added `populate_default` bool argument to :meth:`Column.create <migrate.changeset.schema.ChangesetColumn.create>` which issues corresponding UPDATE statements to set defaults after column creation
 - url parameter can also be an Engine instance (this usage is discouraged though sometimes necessary)
 - added support for SQLAlchemy 0.6 (missing oracle and firebird) by Michael Bayer
 - alter, create, drop column / rename table / rename index constructs now accept `alter_metadata` parameter. If True, it will modify Column/Table objects according to changes. Otherwise, everything will be untouched.

docs/changeset.rst

@@ -39,8 +39,8 @@ Given a standard SQLAlchemy table::
 
 :meth:`Create a column <ChangesetColumn.create>`::
 
- col = Column('col1', String)
- col.create(table)
+ col = Column('col1', String, default='foobar')
+ col.create(table, populate_default=True)
 
  # Column is added to table based on its name
  assert col is table.c.col1

migrate/changeset/schema.py

@@ -485,12 +485,16 @@ class ChangesetColumn(object):
         :param primary_key_name: Creates :class:\
 `~migrate.changeset.constraint.PrimaryKeyConstraint` on this column.
         :param alter_metadata: If True, column will be added to table object.
+        :param populate_default: If True, created column will be \
+populated with defaults
         :type table: Table instance
         :type index_name: string
         :type unique_name: string
         :type primary_key_name: string
         :type alter_metadata: bool
+        :type populate_default: bool
         """
+        self.populate_default = kwargs.pop('populate_default', False)
         self.alter_metadata = kwargs.pop('alter_metadata', DEFAULT_ALTER_METADATA)
         self.index_name = index_name
         self.unique_name = unique_name
@@ -503,6 +507,11 @@ class ChangesetColumn(object):
         engine = self.table.bind
         visitorcallable = get_engine_visitor(engine, 'columngenerator')
         engine._run_visitor(visitorcallable, self, *args, **kwargs)
+
+        if self.populate_default and self.default is not None:
+            stmt = table.update().values({self: engine._execute_default(self.default)})
+            engine.execute(stmt)
+
         return self
 
     def drop(self, table=None, *args, **kwargs):

test/changeset/test_changeset.py

@@ -273,6 +273,20 @@ class TestAddDropColumn(fixture.DB):
         self.assertEqual(u'foobar', row['data'])
 
         col.drop()
+
+    @fixture.usedb()
+    def test_populate_default(self):
+        """Test populate_default=True"""
+        def default():
+            return 'foobar'
+        col = Column('data', String(244), default=default)
+        col.create(self.table, populate_default=True)
+
+        self.table.insert(values={'id': 10}).execute()
+        row = self.table.select(autocommit=True).execute().fetchone()
+        self.assertEqual(u'foobar', row['data'])
+
+        col.drop()
     
     # TODO: test sequence
     # TODO: test quoting

test_db.cfg

@@ -1,14 +0,0 @@
-# test_db.cfg
-# 
-# This file contains a list of connection strings which will be used by 
-# database tests. Tests will be executed once for each string in this file. 
-# You should be sure that the database used for the test doesn't contain any
-# important data. See README for more information.
-# 
-# The string '__tmp__' is substituted for a temporary file in each connection
-# string. This is useful for sqlite tests.
-sqlite:///__tmp__
-postgres://migrate:UPd2icyw@localhost/migrate_test
-mysql://migrate:fTP82sjf@localhost/migrate_test
-oracle://migrate:FdnjJK8s@localhost
-firebird://migrate:BowV7EEm@localhost//var/db/migrate.gdb