Optimizes clusters counter query

Adds an index for batch counting in usage data

changelogs/unreleased/208923-enable-batch-counting-for-some-individual-queries.yml

+---
+title: Optimize clusters counters query performance in usage data
+merge_request: 26887
+author:
+type: performance

db/migrate/20200310123229_add_index_on_enabled_and_provider_type_and_id_to_clusters.rb

+# frozen_string_literal: true
+
+class AddIndexOnEnabledAndProviderTypeAndIdToClusters < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :clusters, [:enabled, :provider_type, :id]
+    remove_concurrent_index :clusters, :enabled
+  end
+
+  def down
+    add_concurrent_index :clusters, :enabled
+    remove_concurrent_index :clusters, [:enabled, :provider_type, :id]
+  end
+end

db/schema.rb

@@ -1125,7 +1125,7 @@ ActiveRecord::Schema.define(version: 2020_03_12_163407) do
     t.integer "management_project_id"
     t.integer "cleanup_status", limit: 2, default: 1, null: false
     t.text "cleanup_status_reason"
-    t.index ["enabled"], name: "index_clusters_on_enabled"
+    t.index ["enabled", "provider_type", "id"], name: "index_clusters_on_enabled_and_provider_type_and_id"
     t.index ["management_project_id"], name: "index_clusters_on_management_project_id", where: "(management_project_id IS NOT NULL)"
     t.index ["user_id"], name: "index_clusters_on_user_id"
   end

lib/gitlab/usage_data.rb

@@ -66,8 +66,8 @@ module Gitlab
             clusters_disabled: count(::Clusters::Cluster.disabled),
             project_clusters_disabled: count(::Clusters::Cluster.disabled.project_type),
             group_clusters_disabled: count(::Clusters::Cluster.disabled.group_type),
-            clusters_platforms_eks: count(::Clusters::Cluster.aws_installed.enabled, batch: false),
-            clusters_platforms_gke: count(::Clusters::Cluster.gcp_installed.enabled, batch: false),
+            clusters_platforms_eks: count(::Clusters::Cluster.aws_installed.enabled),
+            clusters_platforms_gke: count(::Clusters::Cluster.gcp_installed.enabled),
             clusters_platforms_user: count(::Clusters::Cluster.user_provided.enabled),
             clusters_applications_helm: count(::Clusters::Applications::Helm.available),
             clusters_applications_ingress: count(::Clusters::Applications::Ingress.available),