Merge branch '208889-optimize-event-counters' into 'master'

Optimize event counters in usage data

See merge request gitlab-org/gitlab!26444

changelogs/unreleased/208889-optimize-event-counters.yml

+---
+title: Optimize event counters query performance in usage data
+merge_request: 26444
+author:
+type: performance

db/migrate/20200306160521_add_index_on_author_id_and_created_at_to_events.rb

+# frozen_string_literal: true
+
+class AddIndexOnAuthorIdAndCreatedAtToEvents < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :events, [:author_id, :created_at]
+  end
+
+  def down
+    remove_concurrent_index :events, [:author_id, :created_at]
+  end
+end

db/schema.rb

@@ -1616,6 +1616,7 @@ ActiveRecord::Schema.define(version: 2020_03_09_105539) do
     t.string "target_type"
     t.bigint "group_id"
     t.index ["action"], name: "index_events_on_action"
+    t.index ["author_id", "created_at"], name: "index_events_on_author_id_and_created_at"
     t.index ["author_id", "project_id"], name: "index_events_on_author_id_and_project_id"
     t.index ["created_at", "author_id"], name: "analytics_index_events_on_created_at_and_author_id"
     t.index ["group_id"], name: "index_events_on_group_id_partial", where: "(group_id IS NOT NULL)"

lib/gitlab/database/batch_count.rb

@@ -28,7 +28,7 @@ module Gitlab
 
     class BatchCounter
       FALLBACK = -1
-      MIN_REQUIRED_BATCH_SIZE = 2_000
+      MIN_REQUIRED_BATCH_SIZE = 1_250
       MAX_ALLOWED_LOOPS = 10_000
       SLEEP_TIME_IN_SECONDS = 0.01 # 10 msec sleep
       # Each query should take <<500ms https://gitlab.com/gitlab-org/gitlab/-/merge_requests/22705