psql - PostgreSQL: Up and Running - page 49

Timing Executions
You may find it instructive to have psql output the time it took for each query to execute.
Use the \timing command to toggle it on and off.
When that is enabled, each query you run will report the duration at the end. For ex‐
ample, with \timing on , executing SELECT COUNT(*) FROM pg_tables; outputs:
count
--------
73
(1 row)
Time: 18.650 ms
Autocommit Commands
By default, AUTOCOMMIT is on, meaning any SQL command you issue that changes data
will immediately commit. Each command is its own transaction and is irreversible. If
you are running a large batch of precarious updates, you may want a safety net. Start by
turning off autocommit: \set AUTOCOMMIT off . Now, you have the option to roll back
your statements:
UPDATE census . facts SET short_name = 'This is a mistake.' ;
To undo the update, run:
ROLLBACK ;
To make the update permanent, run
COMMIT ;
Don't forget to commit your changes; otherwise, they'll automati‐
cally roll back if you exit psql.
Shortcuts
You can use the \set command to create useful typing shortcuts. Store universally
applicable shortcuts in your psqlrc file. For example, if you use EXPLAIN ANALYZE VER
BOSE once every 10 minutes and you're tired of typing it all out each time, set a variable:
\set eav 'EXPLAIN ANALYZE VERBOSE'
Now, whenever you want to enter EXPLAIN ANALYZE VERBOSE , simply type :eav (the
colon resolves the variable):
:eav SELECT COUNT(*) FROM pg_tables;