How I can merge sub-document (as array) on mongodb collection -

hello have collection:

{     "_id" : objectid("508d27069cc1ae293b36928d"),     "title" : "this title",     "body" : "this body text.",     "created_date" : isodate("2012-10-28t12:41:39.110z"),     "comments" : [         {             "subject" : "this coment 1",             "body" : "this body of comment 1.",             "author_id" : objectid("508d345f9cc1ae293b369296"),             "created_date" : isodate("2012-10-28t13:34:23.929z")         },         {             "subject" : "this coment 2",             "body" : "this body of comment 2.",             "author_id" : objectid("508d34739cc1ae293b369297"),             "created_date" : isodate("2012-10-28t13:34:43.192z")         },         {             "subject" : "this coment 3",             "body" : "this body of comment 3.",             "author_id" : objectid("508d34839cc1ae293b369298"),             "created_date" : isodate("2012-10-28t13:34:59.336z")         }     ] } 

so, on 1 page @ dashboard want see comments, how can that? how can comments each post in single collection, how can identify each comment (for editing or removing)?

upd1:

this doc posts collection. want this:

[     ...,     {          "_generated_id_for_identify": [what data?],          "subject" : "this coment 1",          "body" : "this body of comment 1.",          "author_id" : objectid("508d345f9cc1ae293b369296"),          "created_date" : isodate("2012-10-28t13:34:23.929z")     },     {          "_generated_id_for_identify": [what data?],          "subject" : "this coment 2",          "body" : "this body of comment 2.",          "author_id" : objectid("508d34739cc1ae293b369297"),          "created_date" : isodate("2012-10-28t13:34:43.192z")     },     ...,     {          "_generated_id_for_identify": [what data?],          "subject" : "this coment n",          "body" : "this body of comment n.",          "author_id" : objectid("508d34839cc1ae293b369298"),          "created_date" : isodate("2012-10-28t13:34:59.336z")     },     ... ] 

with aggregate in posts collection , matching "_id" , using unwind in comments , proyection can obtain new collection of comments in results key.

db.posts.aggregate([                    {$match:{_id:objectid("508d27069cc1ae293b36928d")}},                     {$unwind:"$comments"},                     {$project:{                               "_id":{id:"$_id",dt:"$comments.created_date"},                             subject:"$comments.subject",                                body:"$comments.body",                          "autor_id":"$comments.author_id",                      "created_date":"$comments.created_date"}} ]).result 

but simple query matching posts._id obtain post.comments