title: elasticsearch string values vs ids- performance best practices
body: <p>i wonder whats better from performance aspect:
  to store string values in elasticsearch, or to save a map table in mysql(for example), and save the id.
  for example 10M documents with a field 'browser', with all browsers' names,
  or with ids, that i pre-generated and saved in mysql</p>
  
  <p>use case is analyze server traffic</p>
  
  <p>thanks!</p>