title: Postgresql database and table size
body: <p>this is my current table size:</p>
  
  <pre><code>select pg_size_pretty(pg_relation_size('items'));
  
   pg_size_pretty 
  ----------------
  210 GB
  </code></pre>
  
  <p>but when I using pg_databse_size, it shows 1901GB</p>
  
  <pre><code>SELECT pg_size_pretty (pg_database_size ('mydb'));
  
   pg_size_pretty 
  ----------------
   1901 GB
  (1 row)
  </code></pre>
  
  <p>I have been checking all tables, and the items table is the biggest.</p>
  
  <p>My questions is: how to make me understand this situation? Could you explain to me about this condition? Or give me a link to make me understand it.</p>