玩转mongodb（五）：mongodb 3.0+ 查询性能分析

mongodb性能分析方法：explain()

    为了演示的效果，我们先来创建一个有200万个文档的记录。（我自己的电脑耗了15分钟左右插入完成。如果你想插更多的文档也没问题，只要有耐心等就可以了。）

1 for(var i=0;i<2000000;i++){
2     db.person.insert({"name":"ryan"+i,"age":i});
3 }

 

    MongoDB 3.0之后，explain的返回与使用方法与之前版本有了很大的变化，介于3.0之后的优秀特色和我们目前所使用给的是3.0.7版本，本文仅针对MongoDB 3.0+的explain进行讨论。3.0+的explain有三种模式，分别是：queryPlanner、executionStats、allPlansExecution。现实开发中，常用的是executionStats模式，主要分析这种模式。

    给这个person集合创建age键的索引：db.person.createIndex({"age":1})

 1 {
 2     "queryPlanner" : {
 3         "plannerVersion" : 1,
 4         "namespace" : "personmap.person",
 5         "indexFilterSet" : false,
 6         "parsedQuery" : {
 7             "age" : {
 8                 "$lte" : 2000.0
 9             }
10         },
11         "winningPlan" : {
12             "stage" : "FETCH",
13             "inputStage" : {
14                 "stage" : "IXSCAN",
15                 "keyPattern" : {
16                     "age" : 1.0
17                 },
18                 "indexName" : "age_1",
19                 "isMultiKey" : false,
20                 "direction" : "forward",
21                 "indexBounds" : {
22                     "age" : [ 
23                         "[-1.#INF, 2000.0]"
24                     ]
25                 }
26             }
27         },
28         "rejectedPlans" : []
29     },
30     "executionStats" : {
31         "executionSuccess" : true,
32         "nReturned" : 2001,
33         "executionTimeMillis" : 143,
34         "totalKeysExamined" : 2001,
35         "totalDocsExamined" : 2001,
36         "executionStages" : {
37             "stage" : "FETCH",
38             "nReturned" : 2001,
39             "executionTimeMillisEstimate" : 0,
40             "works" : 2002,
41             "advanced" : 2001,
42             "needTime" : 0,
43             "needFetch" : 0,
44             "saveState" : 16,
45             "restoreState" : 16,
46             "isEOF" : 1,
47             "invalidates" : 0,
48             "docsExamined" : 2001,
49             "alreadyHasObj" : 0,
50             "inputStage" : {
51                 "stage" : "IXSCAN",
52                 "nReturned" : 2001,
53                 "executionTimeMillisEstimate" : 0,
54                 "works" : 2002,
55                 "advanced" : 2001,
56                 "needTime" : 0,
57                 "needFetch" : 0,
58                 "saveState" : 16,
59                 "restoreState" : 16,
60                 "isEOF" : 1,
61                 "invalidates" : 0,
62                 "keyPattern" : {
63                     "age" : 1.0
64                 },
65                 "indexName" : "age_1",
66                 "isMultiKey" : false,
67                 "direction" : "forward",
68                 "indexBounds" : {
69                     "age" : [ 
70                         "[-1.#INF, 2000.0]"
71                     ]
72                 },
73                 "keysExamined" : 2001,
74                 "dupsTested" : 0,
75                 "dupsDropped" : 0,
76                 "seenInvalidated" : 0,
77                 "matchTested" : 0
78             }
79         }
80     },
81     "serverInfo" : {
82         "host" : "qinxiongzhou",
83         "port" : 27017,
84         "version" : "3.0.7",
85         "gitVersion" : "6ce7cbe8c6b899552dadd907604559806aa2e9bd"
86     },
87     "ok" : 1.0
88 }

db.getCollection('person').find({"age":{"$lte":2000}}).explain("executionStats")