Take two for MR metrics population background migration

1 files changed, 44 insertions, 0 deletions

diff --git a/db/post_migrate/20180521162137_migrate_remaining_mr_metrics_populating_background_migration.rb b/db/post_migrate/20180521162137_migrate_remaining_mr_metrics_populating_background_migration.rb
new file mode 100644
index 00000000000..0282688fa40
--- /dev/null
+++ b/db/post_migrate/20180521162137_migrate_remaining_mr_metrics_populating_background_migration.rb
@@ -0,0 +1,44 @@
+class MigrateRemainingMrMetricsPopulatingBackgroundMigration < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  BATCH_SIZE = 5_000
+  MIGRATION = 'PopulateMergeRequestMetricsWithEventsData'
+  DELAY_INTERVAL = 10.minutes
+
+  disable_ddl_transaction!
+
+  class MergeRequest < ActiveRecord::Base
+    self.table_name = 'merge_requests'
+
+    include ::EachBatch
+  end
+
+  def up
+    # Perform any ongoing background migration that might still be running. This
+    # avoids scheduling way too many of the same jobs on self-hosted instances
+    # if they're updating GitLab across multiple versions. The "Take one"
+    # migration was executed on 10.4 on
+    # SchedulePopulateMergeRequestMetricsWithEventsData.
+    Gitlab::BackgroundMigration.steal(MIGRATION)
+
+    metrics_not_exists_clause = <<~SQL
+      NOT EXISTS (SELECT 1 FROM merge_request_metrics
+                  WHERE merge_request_metrics.merge_request_id = merge_requests.id)
+    SQL
+
+    relation = MergeRequest.where(metrics_not_exists_clause)
+
+    # We currently have ~400_000 MR records without metrics on GitLab.com.
+    # This means it'll schedule ~80 jobs (5000 MRs each) with a 10 minutes gap,
+    # so this should take ~14 hours for all background migrations to complete.
+    #
+    queue_background_migration_jobs_by_range_at_intervals(relation,
+                                                          MIGRATION,
+                                                          DELAY_INTERVAL,
+                                                          batch_size: BATCH_SIZE)
+  end
+
+  def down
+  end
+end