Database
[{"_class":"com.json.SvnCommitMst","_id":"38735","author":"10662365","commitDate":ISODate("2021-09-30T08:28:01.159Z"),"isLatest":false,"mapSvnFilesMst":[{"_id":ObjectId("618df1b32109446cb6ef58d6"),"commitAction":"MODIFY"}],"message":"Rohit:\n\nUser Repo tool validation changes","projectToolId":92}]
Query
db.collection.aggregate([{$project:{allKeys:{$reduce:{input:{$objectToArray:"$$ROOT"},initialValue:[],in:{$setUnion:["$$value",{$cond:{if:{$eq:[{$type:"$$this.v"},"array"]},then:{$setUnion:[["$$this.k"],{$reduce:{input:"$$this.v",initialValue:[],in:{$setUnion:["$$value",{$let:{vars:{kv:{$objectToArray:"$$this"}},in:"$$kv.k"}}]}}}]},else:["$$this.k"]}}]}}}}}])