Data migration

problem_builder/south_migrations/0002_copy_from_mentoring.py

+# -*- coding: utf-8 -*-
+from django.db.utils import DatabaseError
+from south.db import db
+from south.v2 import DataMigration
+
+
+class Migration(DataMigration):
+
+    def forwards(self, orm):
+        """
+        Copy student data from old table to the new one.
+
+        Problem Builder stores student answers in 'problem_builder_answer'.
+        However earlier versions [may have] used 'mentoring_answer'.
+        If a 'mentoring' app is currently installed on this instance, copy the student data over
+        to the new table in case it is being used.
+        """
+        try:
+            db.execute(
+                'INSERT INTO problem_builder_answer ('
+                'name, student_id, course_id, student_input, created_on, modified_on '
+                ') SELECT '
+                'name, student_id, course_id, student_input, created_on, modified_on '
+                'FROM mentoring_answer'
+            )
+        except DatabaseError:  # Would like to just catch 'Table does not exist' but can't do that in a db-agnostic way
+            print(" - Seems like mentoring_answer does not exist. No data migration needed.")
+
+    def backwards(self, orm):
+        raise RuntimeError("Cannot safely reverse this migration.")
+
+    models = {
+        'problem_builder.answer': {
+            'Meta': {'unique_together': "(('student_id', 'course_id', 'name'),)", 'object_name': 'Answer'},
+            'course_id': ('django.db.models.fields.CharField', [], {'max_length': '50', 'db_index': 'True'}),
+            'created_on': ('django.db.models.fields.DateTimeField', [], {'auto_now_add': 'True', 'blank': 'True'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'modified_on': ('django.db.models.fields.DateTimeField', [], {'auto_now': 'True', 'blank': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '50', 'db_index': 'True'}),
+            'student_id': ('django.db.models.fields.CharField', [], {'max_length': '32', 'db_index': 'True'}),
+            'student_input': ('django.db.models.fields.TextField', [], {'default': "''", 'blank': 'True'})
+        }
+    }
+
+    complete_apps = ['problem_builder']
+    symmetrical = True