Add multiple assignees migration and table population

This will be further required for supporting multi-assignees MRs

1 files changed, 23 insertions, 0 deletions

diff --git a/db/post_migrate/20190322132835_schedule_populate_merge_request_assignees_table.rb b/db/post_migrate/20190322132835_schedule_populate_merge_request_assignees_table.rb
new file mode 100644
index 00000000000..1ecb38e1a86
--- /dev/null
+++ b/db/post_migrate/20190322132835_schedule_populate_merge_request_assignees_table.rb
@@ -0,0 +1,23 @@
+# 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 SchedulePopulateMergeRequestAssigneesTable < ActiveRecord::Migration[5.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  BATCH_SIZE = 10_000
+  MIGRATION = 'PopulateMergeRequestAssigneesTable'
+  DELAY_INTERVAL = 8.minutes.to_i
+
+  disable_ddl_transaction!
+
+  def up
+    say 'Scheduling `PopulateMergeRequestAssigneesTable` jobs'
+    # We currently have ~4_500_000 merge request records on GitLab.com.
+    # This means it'll schedule ~450 jobs (10k MRs each) with a 8 minutes gap,
+    # so this should take ~60 hours for all background migrations to complete.
+    queue_background_migration_jobs_by_range_at_intervals(MergeRequest, MIGRATION, DELAY_INTERVAL, batch_size: BATCH_SIZE)
+  end
+end