MongoDB - $ maxscan選項

Question

C:\>mongo 

C:\>C:\Programs\MongoDB\bin\mongo.exe 
MongoDB shell version: 2.4.8 
connecting to: test 
Welcome to the MongoDB shell! 
[test] 2014-02-26 17:09:35.933 >>> db.people.count(); 
9 
[test] 2014-02-26 17:09:39.10 >>> db.people.find({})._addSpecial("$maxscan", 5); 
{ 
     "_id" : ObjectId("530e61be188483458f1edca7"), 
     "name" : "joe", 
     "random" : 0.7170755963306874 
} 
{ 
     "_id" : ObjectId("530e61c2188483458f1edca8"), 
     "name" : "mark", 
     "random" : 0.6132313262205571 
} 
{ 
     "_id" : ObjectId("530e61c7188483458f1edca9"), 
     "name" : "john", 
     "random" : 0.07292630313895643 
} 
{ 
     "_id" : ObjectId("530e621c188483458f1edcaa"), 
     "name" : "allen", 
     "random" : 0.09901093109510839 
} 
{ 
     "_id" : ObjectId("530e636f188483458f1edcab"), 
     "name" : "kevin", 
     "random" : 0.9719919066410512 
} 
{ 
     "_id" : ObjectId("530e6375188483458f1edcac"), 
     "name" : "nicola", 
     "random" : 0.4626409418415278 
} 
{ 
     "_id" : ObjectId("530e6428188483458f1edcad"), 
     "name" : "peter", 
     "random" : 0.8568310006521642 
} 
{ 
     "_id" : ObjectId("530e642d188483458f1edcae"), 
     "name" : "tim", 
     "random" : 0.5209994465112686 
} 
{ 
     "_id" : ObjectId("530e6437188483458f1edcaf"), 
     "name" : "joseph", 
     "random" : 0.6217151982709765 
} 
[test] 2014-02-26 17:09:51.76 >>> 

我有9個文件在這個集合。
我打電話find查詢以上
選項_addSpecial("$maxscan", 5)。

仍然返回9個文件。
我期待5個文件返回。
它爲什麼這樣表現？

我看了一下文檔這裏

http://docs.mongodb.org/manual/reference/operator/meta/maxScan/

，但我不認爲它提供任何線索。

Answer 1

MongoDB是類型敏感和區分大小寫，這意味着您必須完全按照原樣編寫運算符。你寫的像$maxscan但實際上，根據文檔是$maxScan。