First phase of loading migrations from disk

django/db/migrations/recorder.py

@@ -0,0 +1,64 @@
+import datetime
+from django.db import models
+from django.db.models.loading import BaseAppCache
+
+
+class MigrationRecorder(object):
+    """
+    Deals with storing migration records in the database.
+
+    Because this table is actually itself used for dealing with model
+    creation, it's the one thing we can't do normally via syncdb or migrations.
+    We manually handle table creation/schema updating (using schema backend)
+    and then have a floating model to do queries with.
+
+    If a migration is unapplied its row is removed from the table. Having
+    a row in the table always means a migration is applied.
+    """
+
+    class Migration(models.Model):
+        app = models.CharField(max_length=255)
+        name = models.CharField(max_length=255)
+        applied = models.DateTimeField(default=datetime.datetime.utcnow)
+        class Meta:
+            app_cache = BaseAppCache()
+            app_label = "migrations"
+            db_table = "django_migrations"
+
+    def __init__(self, connection):
+        self.connection = connection
+
+    def ensure_schema(self):
+        """
+        Ensures the table exists and has the correct schema.
+        """
+        # If the table's there, that's fine - we've never changed its schema
+        # in the codebase.
+        if self.Migration._meta.db_table in self.connection.introspection.get_table_list(self.connection.cursor()):
+            return
+        # Make the table
+        editor = self.connection.schema_editor()
+        editor.start()
+        editor.create_model(self.Migration)
+        editor.commit()
+
+    def applied_migrations(self):
+        """
+        Returns a set of (app, name) of applied migrations.
+        """
+        self.ensure_schema()
+        return set(tuple(x) for x in self.Migration.objects.values_list("app", "name"))
+
+    def record_applied(self, app, name):
+        """
+        Records that a migration was applied.
+        """
+        self.ensure_schema()
+        self.Migration.objects.create(app=app, name=name)
+
+    def record_unapplied(self, app, name):
+        """
+        Records that a migration was unapplied.
+        """
+        self.ensure_schema()
+        self.Migration.objects.filter(app=app, name=name).delete()