title: PostgreSQL function gen_random_uuid() not working
body: <p>I get <code>function get_random_uuid() does not exist</code> error when running this SQL:</p>
  
  <p><code>ALTER TABLE "posts" ALTER COLUMN "id" SET DEFAULT gen_random_uuid()</code></p>
  
  <p>I can see <code>pgcrypto</code> module listed in this query <code>select * from pg_available_extensions;</code>. I'm using PostgreSQL 9.4.5 on Ubuntu 14.04.</p>
  
  <p>Did I miss something?</p>