xxxxxxxxxx
db.articles.aggregate(
[ { $match : { author : "dave" } } ]
);
xxxxxxxxxx
{ "_id" : ObjectId("512bc95fe835e68f199c8686"), "author" : "dave", "score" : 80, "views" : 100 }
{ "_id" : ObjectId("512bc962e835e68f199c8687"), "author" : "dave", "score" : 85, "views" : 521 }