Add clean-up migration for RemoveCommaFromWeightSystemNotes

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: 20180704204006) do
+ActiveRecord::Schema.define(version: 20180718100455) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"

ee/changelogs/unreleased/6793-clean-up-after-removecommafromweightsystemnotes-migration.yml

+---
+title: Ensure no weight change system notes end with a superfluous comma
+merge_request: 6571
+author:
+type: other

ee/db/migrate/20180718100455_clean_up_from_weight_system_note_comma_migration.rb

+class CleanUpFromWeightSystemNoteCommaMigration < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  MIGRATION = 'RemoveCommaFromWeightSystemNotes'.freeze
+  BATCH_SIZE = 1000
+
+  class Note < ActiveRecord::Base
+    self.table_name = 'notes'
+
+    include ::EachBatch
+  end
+
+  disable_ddl_transaction!
+
+  def up
+    Gitlab::BackgroundMigration.steal(MIGRATION)
+
+    migrate_inline if weight_system_notes.any?
+  end
+
+  def down
+  end
+
+  private
+
+  def weight_system_notes
+    Note
+      .joins('INNER JOIN system_note_metadata ON notes.id = system_note_metadata.note_id')
+      .where(system: true)
+      .where(system_note_metadata: { action: 'weight' })
+      .where("notes.note LIKE '%,'")
+  end
+
+  def migrate_inline
+    add_concurrent_index(:system_note_metadata, :action, where: "action = 'weight'")
+
+    weight_system_notes.each_batch(of: BATCH_SIZE) do |relation, index|
+      ids = relation.pluck(:id)
+
+      Gitlab::BackgroundMigration::RemoveCommaFromWeightSystemNotes.new.perform(ids)
+    end
+
+    remove_concurrent_index(:system_note_metadata, :action, where: "action = 'weight'")
+  end
+end