Merge branch 'sh-add-missing-acts-as-taggable-indices' into 'master'

changelogs/unreleased/sh-add-missing-acts-as-taggable-indices.yml

+---
+title: Adding missing indexes on taggings table
+merge_request:
+author:
+type: performance

db/migrate/20180306134842_add_missing_indexes_acts_as_taggable_on_engine.rb

+# This migration comes from acts_as_taggable_on_engine (originally 6)
+#
+# It has been modified to handle no-downtime GitLab migrations. Several
+# indexes have been removed since they are not needed for GitLab.
+class AddMissingIndexesActsAsTaggableOnEngine < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :taggings, :tag_id unless index_exists? :taggings, :tag_id
+    add_concurrent_index :taggings, [:taggable_id, :taggable_type] unless index_exists? :taggings, [:taggable_id, :taggable_type]
+  end
+
+  def down
+    remove_concurrent_index :taggings, :tag_id
+    remove_concurrent_index :taggings, [:taggable_id, :taggable_type]
+  end
+end

db/schema.rb

@@ -1734,7 +1734,9 @@ ActiveRecord::Schema.define(version: 20180308052825) do
   end
 
   add_index "taggings", ["tag_id", "taggable_id", "taggable_type", "context", "tagger_id", "tagger_type"], name: "taggings_idx", unique: true, using: :btree
+  add_index "taggings", ["tag_id"], name: "index_taggings_on_tag_id", using: :btree
   add_index "taggings", ["taggable_id", "taggable_type", "context"], name: "index_taggings_on_taggable_id_and_taggable_type_and_context", using: :btree
+  add_index "taggings", ["taggable_id", "taggable_type"], name: "index_taggings_on_taggable_id_and_taggable_type", using: :btree
 
   create_table "tags", force: :cascade do |t|
     t.string "name"