title: Gauge how much time a query actually takes
body: <p>A table has an uuid column. I have two options to generate a uuid value to be inserted into it.</p>
  <ol>
  <li>pre-generate it at API before submitting to DB for <code>INSERT</code></li>
  <li>have PostgreSql generate</li>
  </ol>
  <p>Theoretically option 1 yields better performance, but after the following  simple test in pgAdmin 4 result is not convincing:</p>
  <pre><code>create table public.testuid (uid uuid)
  insert into public.testuid values('e6aec935-824d-47e7-835f-eccb0a4c8485')   -- in ms: 125, 72, 125, 110
  insert into public.testuid values(public.gen_random_uuid()) -- in ms: 130, 80, 112, 101
  </code></pre>
  <p><strong>Update</strong>, thanks to @Bergi, <code>EXPLAIN ANALYZE</code> seems more accurate, and below are the fastest time comparison, pre-gen narrowly outperforms by <strong>0.003ms</strong> (Planning+Execution), may not be benefiting from outside pre-gen.</p>
  <p><a href="https://i.stack.imgur.com/XCJTj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XCJTj.png" alt="enter image description here" /></a>
  <a href="https://i.stack.imgur.com/A140e.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/A140e.png" alt="enter image description here" /></a></p>