Finding all records containing a given subfield in mongodb -

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in mongodb, can find records in collection in database db contain particular field using following query 

var doc = db.collection_name.find({field_name:{$exists:true}})

now consider following document:

{   "somefield":"someval",   "metadata": {"id":"someval",                "client_url":"http://www.something.com"                } }

what query getting records having id field in metadata ?

please help. thank you

you can use dot notation reference sub-document fields

var doc = db.collection_name.find({"metadata.id":{$exists:true}})

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