如何索引我的收藏使用複合多鍵索引

Question

這是我的文件，我想查詢：

{ 
"_id":ObjectId("5062d30522dfae0e11000000"), 
"id_resource" : "147", 
"moment_created" : ISODate("2012-03-22T16:29:21Z"), 
"moment_updated" : ISODate("2012-03-22T16:29:21Z"), 
"users_involved" : [ 
    { 
     "id_user" : "113928869", 
     "state" : "answered", 
     "id_folder" : "0", 
     "is_deleted" : "0" 
    }, 
    { 
     "id_user" : "121624627", 
     "state" : "new", 
     "id_folder" : "0", 
     "is_deleted" : "0" } 
], 
"posts" : [ 
    { 
     "id_author" : "113928869", 
     "post" : "hiohhio", 
     "moment_created" : ISODate("2012-03-22T16:29:21Z") 
    } 
    ] 
} 

，這是我努力確保我的索引：

db.message.ensureIndex({id_resource:1, users_involved : 1}); 

這是我用來查詢我的收藏查詢：

db.message.find({id_resource : "143", "users_involved" : {$elemMatch : {id_user : "101226353", state : "answered"}}}); 

但一人後來解釋我得到這個輸出：

{ 
    "clusteredType" : "ParallelSort", 
    "cursor" : "BasicCursor", 
    "n" : 11, 
    "nChunkSkips" : 0, 
    "nYields" : 8624, 
    "nscanned" : 1461277, 
    "nscannedAllPlans" : 1461277, 
    "nscannedObjects" : 1461277, 
    "nscannedObjectsAllPlans" : 1461277, 
    "millisShardTotal" : 1878, 
    "millisShardAvg" : 939, 
    "numQueries" : 2, 
    "numShards" : 2, 
    "millis" : 1646 

}

getIndexes將返回：

[ 
    { 
      "v" : 1, 
      "key" : { 
        "_id" : 1 
      }, 
      "ns" : "messaging.message", 
      "name" : "_id_" 
    }, 
    { 
      "v" : 1, 
      "key" : { 
        "id_resource" : 1, 
        "users_involved" : 1 
      }, 
      "ns" : "messaging.message", 
      "name" : "id_resource_1_users_involved_1" 
    } 

]

可悲的是，爲什麼我的查詢不使用索引id_resource_1_users_involved_1我不明白。任何人都可以向我解釋爲什麼我的索引不被使用，或者我如何構建我的索引以支持我想要使用的查詢？

THX的時間，並幫助了我

UPDATE

恥辱，在我身邊一個錯字。因此，這裏的實際查詢

{ 
    "clusteredType" : "ParallelSort", 
    "cursor" : "BtreeCursor id_resource_1_users_involved_1", 
    "n" : 5, 
    "nChunkSkips" : 0, 
    "nYields" : 2, 
    "nscanned" : 46868, 
    "nscannedAllPlans" : 93736, 
    "nscannedObjects" : 46868, 
    "nscannedObjectsAllPlans" : 93736, 
    "millisShardTotal" : 281, 
    "millisShardAvg" : 140, 
    "numQueries" : 2, 
    "numShards" : 2, 
    "millis" : 220 

}

所以查詢使用我的索引，但它仍然是緩慢的解釋，也nscanned是相當大的，所以不使用整個索引？我將不得不檢查nscanned匹配使用複合指數從JohnnyHK資源X

消息也得到了很多快得多量：

ensureIndex({id_resource:1, 'users_involved.id_user':1, 'users_involved.state':1}); 

解釋

{ 
    "clusteredType" : "ParallelSort", 
    "cursor" : "BtreeCursor id_resource_1_users_involved.id_user_1_users_involved.state_1", 
    "n" : 5, 
    "nChunkSkips" : 0, 
    "nYields" : 0, 
    "nscanned" : 7, 
    "nscannedAllPlans" : 7, 
    "nscannedObjects" : 7, 
    "nscannedObjectsAllPlans" : 7, 
    "millisShardTotal" : 0, 
    "millisShardAvg" : 0, 
    "numQueries" : 2, 
    "numShards" : 2, 
    "millis" : 1 
} 

所以，如果我想要查詢users_involved數組我必須爲每個查詢建立一個單獨的索引？

採用全陣列還@JohnnyHK像提到：

find({id_resource : "197", "users_involved" : {$elemMatch : {id_user : "128825371", state : "answered", id_folder:"0", is_deleted:"0"}}}).hint("id_resource_1_users_involved_1") 

沒有改善什麼，解釋：

{ 
    "clusteredType" : "ParallelSort", 
    "cursor" : "BtreeCursor id_resource_1_users_involved_1", 
    "n" : 5, 
    "nChunkSkips" : 0, 
    "nYields" : 1, 
    "nscanned" : 46868, 
    "nscannedAllPlans" : 46868, 
    "nscannedObjects" : 46868, 
    "nscannedObjectsAllPlans" : 46868, 
    "millisShardTotal" : 222, 
    "millisShardAvg" : 111, 
    "numQueries" : 2, 
    "numShards" : 2, 
    "millis" : 174 

}

或者也許我還是做錯了？

*也我刪除從解釋響應碎片信息，如果該信息可能是重要的只是說所以

Answer 1

因爲你的化合物索引包括整個users_involved陣列，只能使用的折射率匹配完整的嵌入式文檔時數組的元素。見here。

我想你會更好地服務使用複合索引，其中只包括您打算搜索的users_involved的字段。因此，要麼：

db.message.ensureIndex({id_resource:1, 'users_involved.id_user' : 1}); 

OR

db.message.ensureIndex({id_resource:1, 'users_involved.id_user' : 1, 'users_involved.state' : 1});