From 4f6999fa26ea538084bf433dcc3a78cccafb3a54 Mon Sep 17 00:00:00 2001
From: Oswaldo Ferreira <oswaldo@gitlab.com>
Date: Tue, 4 Dec 2018 17:11:54 -0200
Subject: Populate MR metrics with events table information (migration)

---
 ...4154019_populate_mr_metrics_with_events_data.rb | 38 ++++++++++++++++++++++
 db/schema.rb                                       |  2 +-
 2 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 db/post_migrate/20181204154019_populate_mr_metrics_with_events_data.rb

(limited to 'db')

diff --git a/db/post_migrate/20181204154019_populate_mr_metrics_with_events_data.rb b/db/post_migrate/20181204154019_populate_mr_metrics_with_events_data.rb
new file mode 100644
index 00000000000..1e43e3dd790
--- /dev/null
+++ b/db/post_migrate/20181204154019_populate_mr_metrics_with_events_data.rb
@@ -0,0 +1,38 @@
+# 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 PopulateMrMetricsWithEventsData < ActiveRecord::Migration[4.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  BATCH_SIZE = 10_000
+  MIGRATION = 'PopulateMergeRequestMetricsWithEventsDataImproved'
+  PREVIOUS_MIGRATION = 'PopulateMergeRequestMetricsWithEventsData'
+
+  disable_ddl_transaction!
+
+  def up
+    # Perform any ongoing background migration that might still be running from
+    # previous try (see https://gitlab.com/gitlab-org/gitlab-ce/issues/47676).
+    Gitlab::BackgroundMigration.steal(PREVIOUS_MIGRATION)
+
+    say 'Scheduling `PopulateMergeRequestMetricsWithEventsData` jobs'
+    # It will update around 4_000_000 records in batches of 10_000 merge
+    # requests (running between 5 minutes) and should take around 53 hours to complete.
+    # Apparently, production PostgreSQL is able to vacuum 10k-20k dead_tuples
+    # per minute. So this should give us enough space.
+    #
+    # More information about the updates in `PopulateMergeRequestMetricsWithEventsDataImproved` class.
+    #
+    MergeRequest.all.each_batch(of: BATCH_SIZE) do |relation, index|
+      range = relation.pluck('MIN(id)', 'MAX(id)').first
+
+      BackgroundMigrationWorker.perform_in(index * 8.minutes, MIGRATION, range)
+    end
+  end
+
+  def down
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index d7124100621..5f823d476b3 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20181203002526) do
+ActiveRecord::Schema.define(version: 20181204154019) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
-- 
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