title: Updating child row locks parent row in PostgreSQL (foreign key, 9.1)
body: <p>I have a problem with transaction isolation, let's considering two transactions:</p>
  
  <p>First transaction 1 does an update in a row on table 1, and then, transaction 2 does an update in a row from child table that references the pk from table 1 that was updated in transaction 1, analysing the transactions we can see a lock, transaction 2 will be locked until the transaction 1 be committed or rollebacked, is there a way to avoid this lock? My transaction 1 does not affect table 2, because it was an update in a specific column.
  P.S. My PostgreSQL version is 9.1, I have checked PostgresSQL 9.6 and it does not happen, is there any workaround?</p>