Reschedule commits_count background migrationjprovazn-commits-count-reschedule

We still have >100K unmigrated MergeRequestDiffs
which don't have commits_count set yet (see
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17567#note_61904891)

This migration re-schedules the original background migration.
To assure that records are not processed twice, records with
commits_count set are skipped.

Related to #41698 and !17567

2 files changed, 31 insertions, 1 deletions

diff --git a/db/migrate/20180309121820_reschedule_commits_count_for_merge_request_diff.rb b/db/migrate/20180309121820_reschedule_commits_count_for_merge_request_diff.rb
new file mode 100644
index 00000000000..990759104b0
--- /dev/null
+++ b/db/migrate/20180309121820_reschedule_commits_count_for_merge_request_diff.rb
@@ -0,0 +1,30 @@
+class RescheduleCommitsCountForMergeRequestDiff < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  MIGRATION = 'AddMergeRequestDiffCommitsCount'.freeze
+  BATCH_SIZE = 5000
+  DELAY_INTERVAL = 5.minutes.to_i
+
+  class MergeRequestDiff < ActiveRecord::Base
+    self.table_name = 'merge_request_diffs'
+
+    include ::EachBatch
+  end
+
+  disable_ddl_transaction!
+
+  def up
+    say 'Populating the MergeRequestDiff `commits_count` (reschedule)'
+
+    execute("SET statement_timeout TO '60s'") if Gitlab::Database.postgresql?
+
+    MergeRequestDiff.where(commits_count: nil).each_batch(of: BATCH_SIZE) do |relation, index|
+      start_id, end_id = relation.pluck('MIN(id), MAX(id)').first
+      delay = index * DELAY_INTERVAL
+
+      BackgroundMigrationWorker.perform_in(delay, MIGRATION, [start_id, end_id])
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 75a094bbbb6..970b1ad9948 100644
--- a/db/schema.rb
+++ b/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: 20180308052825) do
+ActiveRecord::Schema.define(version: 20180309121820) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"