compare two fields of same document [duplicate]

Answer 1

You can use $expr which allows the use of aggregation expressions within the query language.

db.collection.find({ "$expr": { "$eq": [ "$_id" , "$md5" ] } })

or with aggregation

db.collection.aggregate([
  { "$match": { "$expr": { "$eq": [ "$_id" , "$md5" ] } } }
])