Add clusters index to improve usage data queries

changelogs/unreleased/add-missing-cluster-usage-data-index.yml

+---
+title: Add clusters index to improve usage data queries
+merge_request: 28626
+author:
+type: performance

db/migrate/20200402001106_add_cluster_type_index_to_clusters.rb

+# frozen_string_literal: true
+
+class AddClusterTypeIndexToClusters < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+  INDEX_NAME = 'index_clusters_on_enabled_cluster_type_id_and_created_at'
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :clusters, [:enabled, :cluster_type, :id, :created_at], name: INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index_by_name :clusters, INDEX_NAME
+  end
+end

db/structure.sql

@@ -9079,6 +9079,8 @@ CREATE INDEX index_clusters_kubernetes_namespaces_on_project_id ON public.cluste
 
 CREATE INDEX index_clusters_on_enabled_and_provider_type_and_id ON public.clusters USING btree (enabled, provider_type, id);
 
+CREATE INDEX index_clusters_on_enabled_cluster_type_id_and_created_at ON public.clusters USING btree (enabled, cluster_type, id, created_at);
+
 CREATE INDEX index_clusters_on_management_project_id ON public.clusters USING btree (management_project_id) WHERE (management_project_id IS NOT NULL);
 
 CREATE INDEX index_clusters_on_user_id ON public.clusters USING btree (user_id);
@@ -13200,6 +13202,7 @@ COPY "schema_migrations" (version) FROM STDIN;
 20200331220930
 20200401095430
 20200401211005
+20200402001106
 20200402123926
 20200402124802
 20200402135250