This is the odd chunk of structural subscriber SQL where we know the bugtarget is Ubuntu so the only relevant structures are distro which also has a package clause:

WITH ss AS
  (SELECT *
   FROM StructuralSubscription
   WHERE StructuralSubscription.subscriber = 3562998)
SELECT BugTask.status,
       BugTask.assignee,
       BugTask.bug,
       BugTask.bugwatch,
       BugTask.date_assigned,
       BugTask.date_closed,
       BugTask.date_confirmed,
       BugTask.date_fix_committed,
       BugTask.date_fix_released,
       BugTask.date_incomplete,
       BugTask.date_inprogress,
       BugTask.date_left_closed,
       BugTask.date_left_new,
       BugTask.date_triaged,
       BugTask.datecreated,
       BugTask.distribution,
       BugTask.distroseries,
       BugTask.heat,
       BugTask.id,
       BugTask.importance,
       BugTask.milestone,
       BugTask.OWNER, BugTask.product,
                      BugTask.productseries,
                      BugTask.sourcepackagename,
                      BugTask.targetnamecache,
                      Bug.access_policy,
                      Bug.date_last_message,
                      Bug.date_last_updated,
                      Bug.date_made_private,
                      Bug.datecreated,
                      Bug.description,
                      Bug.duplicateof,
                      Bug.heat,
                      Bug.heat_last_updated,
                      Bug.id,
                      Bug.latest_patch_uploaded,
                      Bug.message_count,
                      Bug.name,
                      Bug.number_of_duplicates,
                      Bug.OWNER, Bug.private,
                                 Bug.security_related,
                                 Bug.title,
                                 Bug.users_affected_count,
                                 Bug.users_unaffected_count,
                                 Bug.who_made_private
FROM BugTask
JOIN Bug ON BugTask.bug = Bug.id
WHERE BugTask.id IN
    (SELECT BugTask.id
     FROM BugTask
     LEFT JOIN Product ON BugTask.product = Product.id
     AND Product.active
     LEFT JOIN ss ss1 ON BugTask.product = (ss1.product)
     LEFT JOIN ss ss2 ON BugTask.productseries = (ss2.productseries)
     LEFT JOIN ss ss3 ON Product.project = (ss3.project)
     LEFT JOIN ss ss4 ON BugTask.distribution = (ss4.distribution)
     AND (BugTask.sourcepackagename = (ss4.sourcepackagename)
          OR (ss4.sourcepackagename IS NULL))
     LEFT JOIN ss ss5 ON BugTask.distroseries = (ss5.distroseries)
     OR (ss5.distribution) = 0
     AND BugTask.sourcepackagename = (ss5.sourcepackagename)
     LEFT JOIN ss ss6 ON BugTask.milestone = (ss6.milestone), Bug
     WHERE Bug.id = BugTask.bug
       AND BugTask.distribution = 1
       AND (BugTask.status IN (10))
       AND Bug.duplicateof IS NULL
       AND NULL_COUNT(ARRAY[ss1.id, ss2.id, ss3.id, ss4.id, ss5.id, ss6.id]) < 6
       AND (Bug.private = FALSE
            OR EXISTS ( WITH teams AS
                         ( SELECT team
                          FROM TeamParticipation
                          WHERE person = 972620 )
                       SELECT BugSubscription.bug
                       FROM BugSubscription
                       WHERE BugSubscription.person IN
                           (SELECT team
                            FROM teams)
                         AND BugSubscription.bug = Bug.id
                       UNION
                       SELECT BugTask.bug
                       FROM BugTask
                       WHERE BugTask.assignee IN
                           (SELECT team
                            FROM teams)
                         AND BugTask.bug = Bug.id )) )
ORDER BY BugTask.heat DESC, BugTask.id LIMIT 76
OFFSET 0