Upsert and multi of the Update method in MongoDB

The form of update in MongoDB is this:

Db.collectionName.update (query, obj, Upsert, multi);

For Upsert (False by default): If upsert=true, if query finds rows that match the criteria, the rows are modified, and if they are not found, a row is appended to query and obj. If Upsert is false, it is not appended when it is not found.

For multi (false by default): If multi=true, all rows that meet the criteria are modified, otherwise only the first qualifying row is modified.

Upsert and multi of the Update method in MongoDB