PostgreSQL 10 High Performance - Third Edition

Verbose output

If you're interested in what columns are actually being passed around by your queries, an explain plan using VERBOSE will show them:

EXPLAIN VERBOSE SELECT * FROM customers;
QUERY PLAN 
 ----------
Seq Scan on public.customers  (cost=0.00..676.00 rows=20000 width=268)
       Output: customerid, firstname, lastname, address1, address2, city, state, zip, country, region, email, phone, creditcardtype, creditcard, creditcardexpiration, username, password, age, income, gender  

This can be valuable for extremely complicated queries which aren't easy to figure out on your own, or when running queries generated by programs such as an object-relational mapper (ORM) that sometimes include more information than they necessarily need to.