title: What does "tuple (0,79)" in postgres log file mean when a deadlock happened?
body: <p>In postgres log:</p>
  
  <pre><code>2016-12-23 15:28:14 +07 [17281-351 trns: 4280939, vtrns: 3/20] postgres@deadlocks HINT:  See server log for query details.
  2016-12-23 15:28:14 +07 [17281-352 trns: 4280939, vtrns: 3/20] postgres@deadlocks CONTEXT:  while locking tuple (0,79) in relation "account"
  2016-12-23 15:28:14 +07 [17281-353 trns: 4280939, vtrns: 3/20] postgres@deadlocks STATEMENT:  SELECT id FROM account where id=$1 for update;
  </code></pre>
  
  <p>when I provoke a deadlock I can see text: <code>tuple (0,79)</code>.</p>
  
  <p>As I know, a tuple just is several rows in table. But I don't understand what <code>(0,79)</code> means. I have only 2 rows in table account, it's just play and self-learning application.</p>
  
  <p>So what does <code>(0,79)</code> means? </p>