Change discussion_ids on promoted epics notes

Notes on epics promoted from an issue used to get same discussion_id
as the notes from the issue the epic was promoted from, which would
cause problems when trying to reply to the epic discussion.

1 files changed, 62 insertions, 0 deletions

diff --git a/db/post_migrate/20190715193142_migrate_discussion_id_on_promoted_epics.rb b/db/post_migrate/20190715193142_migrate_discussion_id_on_promoted_epics.rb
new file mode 100644
index 00000000000..13f8477f3ea
--- /dev/null
+++ b/db/post_migrate/20190715193142_migrate_discussion_id_on_promoted_epics.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class MigrateDiscussionIdOnPromotedEpics < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  # We have ~5000 unique discussion_ids -> this migration will take about 102 minutes
+  # (5000/100 * 2 minutes + 2 minutes initial delay) on gitlab.com.
+  DOWNTIME = false
+  BATCH_SIZE = 100
+  DELAY_INTERVAL = 2.minutes
+  MIGRATION = 'FixPromotedEpicsDiscussionIds'
+
+  disable_ddl_transaction!
+
+  class SystemNoteMetadata < ActiveRecord::Base
+    self.table_name = 'system_note_metadata'
+    self.inheritance_column = :_type_disabled
+  end
+
+  class Note < ActiveRecord::Base
+    include EachBatch
+
+    has_one :system_note_metadata, class_name: 'MigrateDiscussionIdOnPromotedEpics::SystemNoteMetadata'
+
+    self.table_name = 'notes'
+    self.inheritance_column = :_type_disabled
+
+    def self.fetch_discussion_ids_query
+      promoted_epics_query = Note
+        .joins(:system_note_metadata)
+        .where(system: true)
+        .where(noteable_type: 'Epic')
+        .where(system_note_metadata: { action: 'moved' })
+        .select("DISTINCT noteable_id")
+
+      Note.where(noteable_type: 'Epic')
+        .where(noteable_id: promoted_epics_query)
+        .distinct.pluck(:discussion_id)
+    end
+  end
+
+  def up
+    add_concurrent_index(:system_note_metadata, :note_id, where: "action='moved'", name: 'temp_index_system_note_metadata_on_moved_note_id')
+    add_concurrent_index(:notes, [:id, :noteable_id], where: "noteable_type='Epic' AND system", name: 'temp_index_notes_on_id_and_noteable_id' )
+
+    all_discussion_ids = Note.fetch_discussion_ids_query
+    all_discussion_ids.in_groups_of(BATCH_SIZE, false).each_with_index do |ids, index|
+      delay = DELAY_INTERVAL * (index + 1)
+      BackgroundMigrationWorker.perform_in(delay, MIGRATION, [ids])
+    end
+
+    remove_concurrent_index(:system_note_metadata, :note_id, where: "action='moved'", name: 'temp_index_system_note_metadata_on_moved_note_id')
+    remove_concurrent_index(:notes, [:id, :noteable_id], where: "noteable_type='Epic' AND system", name: 'temp_index_notes_on_id_and_noteable_id')
+  end
+
+  def down
+    # no-op
+  end
+end