1 files changed, 87 insertions, 0 deletions
diff --git a/db/post_migrate/20170324160416_migrate_user_activities_to_users_last_activity_on.rb b/db/post_migrate/20170324160416_migrate_user_activities_to_users_last_activity_on.rb
new file mode 100644
index 00000000000..9ad36482c8a
--- /dev/null
+++ b/db/post_migrate/20170324160416_migrate_user_activities_to_users_last_activity_on.rb
@@ -0,0 +1,87 @@
+class MigrateUserActivitiesToUsersLastActivityOn < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  DOWNTIME = false
+  USER_ACTIVITY_SET_KEY = 'user/activities'.freeze
+  ACTIVITIES_PER_PAGE = 100
+  TIME_WHEN_ACTIVITY_SET_WAS_INTRODUCED = Time.utc(2016, 12, 1)
+
+  def up
+    return if activities_count(TIME_WHEN_ACTIVITY_SET_WAS_INTRODUCED, Time.now).zero?
+
+    day = Time.at(activities(TIME_WHEN_ACTIVITY_SET_WAS_INTRODUCED, Time.now).first.second)
+
+    transaction do
+      while day <= Time.now.utc.tomorrow
+        persist_last_activity_on(day: day)
+        day = day.tomorrow
+      end
+    end
+  end
+
+  def down
+    # This ensures we don't lock all users for the duration of the migration.
+    update_column_in_batches(:users, :last_activity_on, nil) do |table, query|
+      query.where(table[:last_activity_on].not_eq(nil))
+    end
+  end
+
+  private
+
+  def persist_last_activity_on(day:, page: 1)
+    activities_count = activities_count(day.at_beginning_of_day, day.at_end_of_day)
+
+    return if activities_count.zero?
+
+    activities = activities(day.at_beginning_of_day, day.at_end_of_day, page: page)
+
+    update_sql =
+      Arel::UpdateManager.new(ActiveRecord::Base).
+        table(users_table).
+        set(users_table[:last_activity_on] => day.to_date).
+        where(users_table[:username].in(activities.map(&:first))).
+        to_sql
+
+    connection.exec_update(update_sql, self.class.name, [])
+
+    unless last_page?(page, activities_count)
+      persist_last_activity_on(day: day, page: page + 1)
+    end
+  end
+
+  def users_table
+    @users_table ||= Arel::Table.new(:users)
+  end
+
+  def activities(from, to, page: 1)
+    Gitlab::Redis.with do |redis|
+      redis.zrangebyscore(USER_ACTIVITY_SET_KEY, from.to_i, to.to_i,
+        with_scores: true,
+        limit: limit(page))
+    end
+  end
+
+  def activities_count(from, to)
+    Gitlab::Redis.with do |redis|
+      redis.zcount(USER_ACTIVITY_SET_KEY, from.to_i, to.to_i)
+    end
+  end
+
+  def limit(page)
+    [offset(page), ACTIVITIES_PER_PAGE]
+  end
+
+  def total_pages(count)
+    (count.to_f / ACTIVITIES_PER_PAGE).ceil
+  end
+
+  def last_page?(page, count)
+    page >= total_pages(count)
+  end
+
+  def offset(page)
+    (page - 1) * ACTIVITIES_PER_PAGE
+  end
+end