Changeset 217

Timestamp:

06/13/06 21:20:26

Author:

fumanchu

Message:

Added schema.assert_version method.

Files:

• trunk/schemas.py (modified) (2 diffs)

trunk/schemas.py

@@ -16 +16 @@
-
-class Schema(object):
+    """Schema versioning tool for Dejavu Units.
+    
+    Make a subclass of this base class to manage changes to your model layer
+    (Units and UnitProperties) as your application grows. Each time you make
+    a change to your model, add a new upgrade_to_X method to your subclass,
+    and increment the "latest" attribute to match:
+    
+    class MySchema(dejavu.Schema):
+        
+        latest = 1
+        
+        def upgrade_to_1(self):
+            # Remove Employee.ZipCode and add .StartDate
+            self.arena.drop_property(Employee, "ZipCode")
+            self.arena.add_property(Employee, "StartDate")
+    
+    Then, in your deployment scripts, you can choose how much you want to
+    automate control of the schema.
+    
+        schema = MySchema(myarena)
+        
+        if cmd == 'upgrade':
+            schema.upgrade()
+        elif cmd == 'install':
+            schema.assert_storage()
+        else:
+            schema.assert_version()
+    """
-    
-    guid = ""
@@ -114 +142 @@
-            if not self.arena.has_storage(cls):
-                self.arena.create_storage(cls)
+    
+    def assert_version(self):
+        """Die if schema version is missing or out of sync."""
+        msg = None
+        if not self.versioned:
+            msg = ("This application now uses a versioned schema, but the "
+                   "installed version could not be determined. You must "
+                   "either install the application or manually set the "
+                   "version number.")
+        if self.deployed > self.latest:
+            msg = "Deployed version is greater than the latest version!?!"
+        if self.deployed < self.latest:
+            msg = ("Deployed version is less than the latest version. "
+                   "You must upgrade before proceeding.")
+        if msg:
+            raise errors.DejavuError(msg)
+