Set NULL autokarma on Updates to True if auto_karma is non-NULL.

fixes #950

alembic/versions/5110dfc1a01a_set_autokarma_to_true_for_updates_.py

@@ -0,0 +1,32 @@
+"""Set NULL autokarma to True for Updates that have non-NULL stable karma thresholds.
+
+Revision ID: 5110dfc1a01a
+Revises: 37f38ddc4c8d
+Create Date: 2016-09-24 02:53:42.025785
+
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '5110dfc1a01a'
+down_revision = '37f38ddc4c8d'
+
+
+def upgrade():
+    """Set NULL autokarma to True for Updates that have non-NULL stable karma thresholds."""
+    # Build a fake mini version of the updates table so we can form an UPDATE statement.
+    updates = sa.sql.table('updates', sa.sql.column('autokarma', sa.Boolean),
+                           sa.sql.column('stable_karma', sa.Integer))
+    # Set autokarma to True if there is a stable threshold set and autokarma is None.
+    op.execute(
+        updates.update().where(
+            updates.c.stable_karma != None).where(updates.c.autokarma == None).values(
+                {'autokarma': True}))
+
+
+def downgrade():
+    """There isn't a way to downgrade this migration."""
+    pass