There can be multiple pre-commands:

• setting timezone (option `timezone`)
• requesting server version by command, not trusting initial handshake (option `forceVersionCheck`)
• executing initial queries (option `initSql`)
• setting default query timeout (option `queryTimeout`)

When using callback connection, other commands can be programmed by application before connection is really established. In this particular case, the pre-commands might not be executed still.

example :

  const mariadb = require('mariadb/callback');

  const conn = mariadb.createConnection({host: 'mydb.com', user:'myUser', password: 'myPwd'});

  conn.query("SELECT 1 as val", (err, rows) => { ...}

conn is a connection object, but authentication isn't still done (it will only be done when 'connect' event is emited)

Correction is to ensure pre-command are executed before any "quick commands"