Difference between set, \\set and \\pset in psql

Question

I get a little confused some times when working with psql between when to use a set vs. \set vs. \pset. I think that:

• set is for session variables on my connection to the db. For example SET ROLE dba;
• \set is for local variables for this psql session. For example \set time 'select current_timestamp'
• \pset is for psql settings for this psql session. For example '\pset border 2'

But, I've never found what I thought was a good explanation of each. Are my assumptions above correct?

I'm using PostgreSQL 9.4

Answer 1

Basically correct. The important difference is that SET is an SQL command while the other two are psql meta-commands - indicated by the prefixed \.

• SET is an SQL command to change run-time parameters. It is executed on the server and has nothing to do with psql per se.

• \set is a psql meta-command and, per documentation:

  Sets the psql variable name to value [...]

  Note: This command is unrelated to the SQL command SET.

• \pset is another psql meta-command. Per documentation:

  This command sets options affecting the output of query result tables