More efficient single account retrieval (0.9ms vs 50ms before)

app/models/account.rb

@@ -187,7 +187,7 @@ class Account < ApplicationRecord
 
     def find_remote!(username, domain)
       return if username.blank?
-      where(arel_table[:username].matches(username.gsub(/[%_]/, '\\\\\0'))).where(domain.nil? ? { domain: nil } : arel_table[:domain].matches(domain.gsub(/[%_]/, '\\\\\0'))).take!
+      where('lower(accounts.username) = ?', username.downcase).where(domain.nil? ? { domain: nil } : 'lower(accounts.domain) = ?', domain&.downcase).take!
     end
 
     def find_local(username)

db/migrate/20170322021028_add_lowercase_index_to_accounts.rb

@@ -0,0 +1,9 @@
+class AddLowercaseIndexToAccounts < ActiveRecord::Migration[5.0]
+  def up
+    execute 'CREATE INDEX index_accounts_on_username_and_domain_lower ON accounts (lower(username), lower(domain))'
+  end
+
+  def down
+    remove_index :accounts, name: 'index_accounts_on_username_and_domain_lower'
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170318214217) do
+ActiveRecord::Schema.define(version: 20170322021028) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -45,6 +45,7 @@ ActiveRecord::Schema.define(version: 20170318214217) do
     t.boolean  "locked",                  default: false, null: false
     t.string   "header_remote_url",       default: "",    null: false
     t.index "(((setweight(to_tsvector('simple'::regconfig, (display_name)::text), 'A'::\"char\") || setweight(to_tsvector('simple'::regconfig, (username)::text), 'B'::\"char\")) || setweight(to_tsvector('simple'::regconfig, (COALESCE(domain, ''::character varying))::text), 'C'::\"char\")))", name: "search_index", using: :gin
+    t.index "lower((username)::text), lower((domain)::text)", name: "index_accounts_on_username_and_domain_lower", using: :btree
     t.index ["username", "domain"], name: "index_accounts_on_username_and_domain", unique: true, using: :btree
   end