Question

我使用Mongo Java驱动程序编写了一个MongoDB索引，如下所示：

MongoClient mongoClient = new MongoClient("localhost", 27017);

DB db = mongoClient.getDB("test");

DBCollection coll = db.getCollection("indexdemo");

coll.createIndex(new BasicDBObject("code",1));

for (int ii=0;ii<100000;ii++) {

DBObject doc = new BasicDBObject("code", ii);

coll.insert(doc);

}

当我执行索引的解释计划（MongoDB 3.x）时，似乎可以识别索引边界但是totalKeysExamined是0并且totalDocsExamined也是0

db.indextest.find({code: 5000}).explain("executionStats")
{  
. . . .
   "executionStats":{  
      "executionSuccess":true,
      "nReturned":0,
      "executionTimeMillis":0,
      "totalKeysExamined":0,
      "totalDocsExamined":0,
      "executionStages":{  
         "stage":"FETCH",
         "nReturned":0,
         "executionTimeMillisEstimate":0,
         "works":1,
         "advanced":0,
         "needTime":0,
         "needFetch":0,
         "saveState":0,
         "restoreState":0,
         "isEOF":1,
         "invalidates":0,
         "docsExamined":0,
         "alreadyHasObj":0,
         "inputStage":{  
            "stage":"IXSCAN",
            "nReturned":0,
            "executionTimeMillisEstimate":0,
            "works":1,
            "advanced":0,
            "needTime":0,
            "needFetch":0,
            "saveState":0,
            "restoreState":0,
            "isEOF":1,
            "invalidates":0,
            "keyPattern":{  
               "code":1
            },
            "indexName":"userid_1",
            "isMultiKey":false,
            "direction":"forward",
            "indexBounds":{  
               "code":[  
                  "[\"1111\", \"1111\"]"
               ]
            },
            "keysExamined":0,
            "dupsTested":0,
            "dupsDropped":0,
            "seenInvalidated":0,
            "matchTested":0
         }
      },
      "allPlansExecution":[  

      ]
   },

Answer 1

如果按索引只有一个匹配，则defenitely得到totalKeysExamined = 1和totalDocsExamined = 1。

检查您是否使用了正确的集合：db.getCollection（＆＃34; indexdemo ＆＃34;） vs db。 indextest .find（）
确保db.indextest.find（{code：5000}）返回1个文档。到目前为止，你已经nReturned = 0。
检查索引名称：通常如果您创建索引{code：1}，它将被命名为code_1，您的统计信息显示＆＃34; indexName＆＃34;：＆＃34; userid_1＆＃34;

MongoDB索引：totalDocsExamined返回0

1 个答案: