Remove project_mirror_data created_at and updated_at columns

ee/app/models/ee/project_import_state.rb

@@ -4,6 +4,9 @@ module EE
     extend ::Gitlab::Utils::Override
 
     prepended do
+      include IgnorableColumn
+      ignore_column :created_at, :updated_at
+
       BACKOFF_PERIOD = 24.seconds
       JITTER = 6.seconds
 

ee/db/migrate/20170509153720_create_project_mirror_data_ee.rb

@@ -21,9 +21,7 @@ class CreateProjectMirrorDataEE < ActiveRecord::Migration
             0 AS retry_count,
             CAST(NULL AS #{timestamp}) AS last_update_started_at,
             CAST(NULL AS #{timestamp}) AS last_update_scheduled_at,
-            NOW() AS next_execution_timestamp,
-            NOW() AS created_at,
-            NOW() AS updated_at
+            NOW() AS next_execution_timestamp
           FROM projects
           WHERE mirror IS TRUE
         );

ee/db/post_migrate/20170530111134_ensure_project_mirror_data.rb

@@ -12,17 +12,13 @@ class EnsureProjectMirrorData < ActiveRecord::Migration
         retry_count,
         last_update_started_at,
         last_update_scheduled_at,
-        next_execution_timestamp,
-        created_at,
-        updated_at
+        next_execution_timestamp
       )
       SELECT id AS project_id,
         0 AS retry_count,
         CAST(NULL AS TIMESTAMP) AS last_update_started_at,
         CAST(NULL AS TIMESTAMP) AS last_update_scheduled_at,
-        NOW() AS next_execution_timestamp,
-        NOW() AS created_at,
-        NOW() as updated_at
+        NOW() AS next_execution_timestamp
       FROM projects
       WHERE mirror IS TRUE
       AND NOT EXISTS (

ee/db/post_migrate/20180509091305_remove_project_mirror_data_created_at_updated_at.rb

+class RemoveProjectMirrorDataCreatedAtUpdatedAt < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def up
+    # A project_mirror_data table created in EE would have these columns, but
+    # one created in CE wouldn't. We don't actually need them, so let's remove them.
+    remove_column :project_mirror_data, :created_at if column_exists?(:project_mirror_data, :created_at)
+    remove_column :project_mirror_data, :updated_at if column_exists?(:project_mirror_data, :updated_at)
+  end
+
+  def down
+    # The columns do not need to be re-added; no application logic ever used them,
+    # and migrations that did have been modified to no longer do so.
+  end
+end