1.5Gb db-logs user log file

A user log file within db-logs has recently exploded, adding 29million identical lines… or 5 per second, all stating:
“02-13-2019 @ 13:17:43 – Checking if username exists….”

The problem started when, for a brief period, we allowed users to create their own username. We have now discontinued that practice (since obviously we could not ensure users chose moodle compatible usernames). I assume I can delete the log file .. but I also assume I must also do something else to stop this process?

Extract from log file:

02-12-2019 @ 14:10:23 – User enrolled for courses – a:1:{i:0;s:4:”6410″;}
02-12-2019 @ 14:10:25 – Check Line Items for Order ID – 7048
02-12-2019 @ 14:10:25 – Courses IDs from Line Items a:1:{i:0;s:4:”6410″;}
02-13-2019 @ 08:44:36 – Start creating/updating moodle user, Updating: 1
02-13-2019 @ 13:17:40 – Link Moodle User for User ID 761
02-13-2019 @ 13:17:40 – Log from WooIntegration
02-13-2019 @ 13:17:40 – User Object JSON Encoded : {“data”:{“ID”:”761″,”user_login”:”richard ankrah”,”user_pass”:”$P$BkKXGFbfgX5APQBY\/4be05eIVgK1Cz0″,”user_nicename”:”richard-ankrah”,”user_email”:”[email protected]”,”user_url”:””,”user_registered”:”2019-02-13 13:17:40″,”user_activation_key”:””,”user_status”:”0″,”display_name”:”Richard Ankrah”},”ID”:761,”caps”:{“customer”:true},”cap_key”:”wpgn_capabilities”,”roles”:[“customer”],”allcaps”:{“read”:true,”edit_posts”:false,”delete_posts”:false,”customer”:true},”filter”:null}
02-13-2019 @ 13:17:41 – Start creating/updating moodle user, Updating: 0
02-13-2019 @ 13:17:41 – Checking if username exists….
02-13-2019 @ 13:17:41 – Checking if username exists….
02-13-2019 @ 13:17:41 – Checking if username exists….
02-13-2019 @ 13:17:41 – Checking if username exists….
02-13-2019 @ 13:17:42 – Checking if username exists….
02-13-2019 @ 13:17:42 – Checking if username exists….
02-13-2019 @ 13:17:42 – Checking if username exists….
02-13-2019 @ 13:17:42 – Checking if username exists….
02-13-2019 @ 13:17:43 – Checking if username exists….