mongodb上在嵌套子文档的文档上面建立索引

发布时间：2023-10-19 16:02:44 所属栏目：系统来源：

导读：mongodb中在嵌套子文档的文档上面建立索引

在mongodb的test库：

> db.data.insert({name:"1616",info:{url:"http://www.1616.net/",city:"beijing"}});

> db.data.insert({name:"hao123",info:{url:"http:

mongodb中在嵌套子文档的文档上面建立索引

在mongodb的test库：

> db.data.insert({name:"1616",info:{url:"http://www.1616.net/",city:"beijing"}});

> db.data.insert({name:"hao123",info:{url:"http://www.hao123.com/",city:"beijing"}});

> db.data.insert({name:"ll4la",info:{url:"http://www.114la.com/",city:"dongguan"}});

2.对字段 info 创建索引：

> db.data.ensureIndex({info: 1});

3.data表的索引查询：

rs0:PRIMARY> db.data.getIndexes()

[

        {

                "v" : 1,

                "key" : {

                        "_id" : 1

                },

                "name" : "_id_",

                "ns" : "test.data"

        },

        {

                "v" : 1,

                "key" : {

                        "info" : 1

                },

                "name" : "info_1",

                "ns" : "test.data"

        }

]

4.索引的用法：

以下查询是可以用到info的索引的：

>db.data.find({info: {url:"http://www.1616.net/", city:"beijing"}});

>db.data.find({info: {url:"http://www.1616.net/"} });

>db.data.find({info: {city:"beijing"});

可以使用query.explain()查看索引的使用：



rs0:PRIMARY> db.data.find({info: {city:"beijing"}}).explain()

{

        "queryPlanner" : {

                "plannerVersion" : 1,

                "namespace" : "test.data",

                "indexFilterSet" : false,

                "parsedQuery" : {

                        "info" : {

                                "$eq" : {

                                        "city" : "beijing"

                                }

                        }

                },

                "winningPlan" : {

                        "stage" : "FETCH",

                        "inputStage" : {

                                "stage" : "IXSCAN",

                                "keyPattern" : {

                                        "info" : 1

                                },

                                "indexName" : "info_1",

                                "isMultiKey" : false,

                                "isUnique" : false,

                                "isSparse" : false,

                                "isPartial" : false,

                                "indexVersion" : 1,

                                "direction" : "forward",

                                "indexBounds" : {

                                        "info" : [

                                                "[{ city: \"beijing\" }, { city: \"beijing\" }]"

                                        ]

                                }

                        }

                },

                "rejectedPlans" : [ ]

        },

        "serverInfo" : {

                "host" : "mycentos.WORKGROUP",

                "port" : 27017,

                "version" : "3.2.8",

                "gitVersion" : "ed70e33130c977bda0024c125b56d159573dbaf0"

        },

        "ok" : 1

}

但是这样的查询就不行：

>db.data.find({"info.city":"beijing"});    //字段部分必须加引号

>db.data.find({info.url:"..."});

这样的查询语句，只能使用类似的组合索引：

> db.data.ensureIndex({"info.url":1, "info.city":1});

5.组合索引

> db.data.ensureIndex({"info.url":1, "info.city":1});

即使查询时，与定义的排序相反，也是可以使用索引扫描的。

rs0:PRIMARY> db.data.find({"info.url": /http:*/i}).sort({"info.url": -1, "info.city":-1}).explain()

{

        "queryPlanner" : {

                "plannerVersion" : 1,

                "namespace" : "test.data",

                "indexFilterSet" : false,

                "parsedQuery" : {

                        "info.url" : /http:*/i

                },

                "winningPlan" : {

                        "stage" : "FETCH",

                        "inputStage" : {

                                "stage" : "IXSCAN",

                                "filter" : {

                                        "info.url" : /http:*/i

                                },

                                "keyPattern" : {

                                        "info.url" : 1,

                                        "info.city" : 1

                                },

                                "indexName" : "info.url_1_info.city_1",

                                "isMultiKey" : false,

                                "isUnique" : false,

                                "isSparse" : false,

                                "isPartial" : false,

                                "indexVersion" : 1,

                                "direction" : "backward",

                                "indexBounds" : {

                                        "info.url" : [

                                                "[/http:*/i, /http:*/i]",

                                                "({}, \"\"]"

                                        ],

                                        "info.city" : [

                                                "[MaxKey, MinKey]"

                                        ]

                                }

                        }

                },

                "rejectedPlans" : [ ]

        },

        "serverInfo" : {

                "host" : "mycentos.WORKGROUP",

                "port" : 27017,

                "version" : "3.2.8",

                "gitVersion" : "ed70e33130c977bda0024c125b56d159573dbaf0"

        },

        "ok" : 1

}

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