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":"$$ROOT"},"initialValue":[],"in":{"$concatArrays":["$$value",["$$this.k"]]}}}}}])