title: how to reduce toast_tuple_threshold in PostgreSQL?
body: <p>OS: RHEL 7.2
  PostgreSQL Version 9.6</p>
  
  <p>I want toast to compress data. The average record length is around 500 Bytes in my tables. Although the columns show storage as extended, yet no compression is happening. Hence I want to modify toast_tuple_threshold to 500 bytes. Which file holds this value? And do we need to modify any other parameter?</p>