Add index to labels for `type` and project_id`

When loading pages that display the number of open issues, the backend runs a query such as: ```sql SELECT "labels"."id" FROM "labels" WHERE "labels"."type" IN ('ProjectLabel') AND "labels"."project_id" = 1000 ``` This results in an entire scan of the `labels` table. To optimize performance, add the appropriate index to the table. Closes #27676

Add index to labels for `type` and project_id`
1e97a6df · Stan Hu · 8a333d45 · 1e97a6df · 1e97a6df
Commit 1e97a6df authored Feb 04, 2017 by Stan Hu
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20170204181513_add_index_to_labels_for_type_and_project.rb ...0170204181513_add_index_to_labels_for_type_and_project.rb +11 -0

schema.rb db/schema.rb +2 -1

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--- a/db/migrate/20170204181513_add_index_to_labels_for_type_and_project.rb
+++ b/db/migrate/20170204181513_add_index_to_labels_for_type_and_project.rb
+class AddIndexToLabelsForTypeAndProject < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def change
+    add_concurrent_index :labels, [:type, :project_id]
+  end
+end
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.

-ActiveRecord::Schema.define(version: 20170130204620) do
+ActiveRecord::Schema.define(version: 20170204181513) do

  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"
@@ -576,6 +576,7 @@ ActiveRecord::Schema.define(version: 20170130204620) do
  end

  add_index "labels", ["group_id", "project_id", "title"], name: "index_labels_on_group_id_and_project_id_and_title", unique: true, using: :btree
+  add_index "labels", ["type", "project_id"], name: "index_labels_on_type_and_project_id", using: :btree

  create_table "lfs_objects", force: :cascade do |t|
    t.string "oid", null: false