Remove default value for lock_version

db/migrate/20160827011312_ensure_lock_version_has_no_default.rb

@@ -0,0 +1,16 @@
+class EnsureLockVersionHasNoDefault < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def up
+    change_column_default :issues, :lock_version, nil
+    change_column_default :merge_requests, :lock_version, nil
+
+    execute('UPDATE issues SET lock_version = 1 WHERE lock_version = 0')
+    execute('UPDATE merge_requests SET lock_version = 1 WHERE lock_version = 0')
+  end
+
+  def down
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160824103857) do
+ActiveRecord::Schema.define(version: 20160827011312) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"