title: Postgres pg_dump effect on production DB
body: <p>Is it possible to query how many multiversioned rows are there in a db ?</p>
  
  <p>We want to measure the impact of <strong>pg_dump</strong> on a production database, and to suspend it in case of need: is it creating too many multiversioned rows?</p>
  
  <p>Thanks in advance</p>