I wrote a little bash script that demonstrates how to query to bacula tables in postgresql database and purge volumes for a given job.   The same can be accomplished for mysql

In the example below,  I am searching for job ID 8431.

-----------code-----------------

#!/bin/bash

volumes=`psql -U bacula bacula -c "select distinct  media.volumename from media,jobmedia where jobmedia.mediaid = media.mediaid and jobmedia.jobid=8431 order by media.volumename;" | grep -v volumename  | grep  -v '(' | grep -v '-'`

for vol in $volumes

do

echo "Purging  volume $vol"

/usr/sbin/bconsole  << EOF

purge  volume=$vol

EOF