with done_bugs as (
    select date_trunc('month', last_modified) as last_modified_month, id, done_email, severity
    from archived_bugs
    where status = 'done'
    union
    select date_trunc('month', last_modified) as last_modified_month, id, done_email, severity
    from bugs
    where status = 'done'
), my_bugs as (
    select * from done_bugs
    where done_email = 'cjwatson@debian.org'
    and severity >= 'serious'
)
select to_char(month.month, 'YYYY-MM'), count(*) filter (where my_bugs.last_modified_month = month.month)
from generate_series((select min(last_modified_month) from my_bugs), (select max(last_modified_month) from my_bugs), '1 month') month
left join my_bugs on month.month = my_bugs.last_modified_month
group by 1
order by 1 desc
;