Example using Postgres slow log 1) Edit Postgres config and turn on full statement debugging (eg /etc/postgresql/10/main/postgresql.conf) log_min_duration_statement = 0 2) restart postgres sudo service postgresql restart 3) tail the postgres logs tail -f /var/log/postgresql/postgresql-10-main.log 4) do anything on the site, confirm you see raw sql 5) Visit debugging page and set debugsqltrace to 1 /admin/settings.php?section=debugging 6) Confirm you can see 1 line of the code that called the dml function 7) Rinse and repeat with setting to 2 lines and all lines 8) confirm in the sql that you can see the exact line and line number of the php code which calls the DB method: 2020-06-02 17:11:49.340 AEST [15386] moodlelocal@moodlelocal LOG: duration: 0.538 ms execute <unnamed>: DECLARE crs1 NO SCROLL CURSOR WITH HOLD FOR SELECT f.filter, fc.name, fc.value FROM mdl_filter_active f LEFT JOIN mdl_filter_config fc ON fc.filter = f.filter AND fc.contextid = f.contextid WHERE f.contextid = $1 AND f.active != $2 ORDER BY f.sortorder -- line 801 of /lib/filterlib.php: call to pgsql_native_moodle_database->get_recordset_sql() -- line 281 of /lib/filterlib.php: call to filter_get_globally_enabled_filters_with_config() Rinse and repeat for other DBs as needed