Launch specs with rake spec so the db is reset !
# find all jobs where tags are either id1, id2 or id3 => id1 || id2 || id3
#Job.all(:conditions => {'tag_ids' => [id1, id2, id3]})
#find all jobs where tags contains id1, id2 AND id3 => id1 && id2 && id3
#Job.all(:conditions => {'tag_ids' => {'$all' => [id1, id2, id3] }})