move core schema to class files

classes/Schema_version.php

@@ -3,7 +3,7 @@
  * Table Definition for schema_version
  */
 
-class Schema_version extends Memcached_DataObject
+class Schema_version extends Managed_DataObject
 {
     ###START_AUTOCODE
     /* the code below is auto generated do not remove the above tag */
@@ -19,4 +19,17 @@ class Schema_version extends Memcached_DataObject
 
     /* the code above is auto generated do not remove the tag below */
     ###END_AUTOCODE
+
+    public static function schemaDef()
+    {
+        return array(
+            'description' => 'To avoid checking database structure all the time, we store a checksum of the expected schema info for each table here. If it has not changed since the last time we checked the table, we can leave it as is.',
+            'fields' => array(
+                'table_name' => array('type' => 'varchar', 'length' => '64', 'not null' => true, 'description' => 'Table name'),
+                'checksum' => array('type' => 'varchar', 'length' => '64', 'not null' => true, 'description' => 'Checksum of schema array; a mismatch indicates we should check the table more thoroughly.'),
+                'modified' => array('type' => 'timestamp', 'not null' => true, 'description' => 'date this record was modified'),
+            ),
+            'primary key' => array('table_name'),
+        );
+    }
 }