title: Postgresql: Which is faster: query with OR clause, or two separate queries?
body: <p>Between these two queries, which one is faster for the database to execute?</p>
  
  <pre><code>select a, b, c from t where x = y or x = z;
  </code></pre>
  
  <p>vs.</p>
  
  <pre><code>select a, b, c from t where x = y;
  select a, b, c from t where x = z;
  </code></pre>
  
  <p>Either one is fine for my application because the results will be put into a map that will automatically remove duplicates. So then I wonder if there is a technical reason one is more preferable than the other.</p>