title: Best PostgreSQL datatype for storing key-value maps?
body: <p>I'd like to store a simple map of key-value strings as a field in my PostgreSQL table. I intend to treat the map as a whole; i.e, always select the entire map, and never query by its keys nor values.</p>
  
  <p>I've read articles comparing between <code>hstore</code>, <code>json</code> and <code>jsonb</code>, but those didn't help me choose which data-type is most fitting for my requirements, which are:</p>
  
  <ul>
  <li>Only key-value, no need for nesting.</li>
  <li>Only strings, no other types nor <code>null</code>.</li>
  <li>Storage efficiency, given my intended use for the field.</li>
  <li>Fast parsing of the queried maps.</li>
  </ul>
  
  <p>What data-type would best fit my use case?</p>