Indexing in MongoDB on documents embedded in a subdocument

1. In the MongoDB Test library:

> 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. Create an index on the field info:

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

Index query for 3.data tables:

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. Usage of the index:

The following query is available with the index of info:

>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"});

You can use Query.explain () to view the use of the index:

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

}

But such a query will not work:

>db.data.find ({"info.city": "Beijing"}); Field part must be quoted

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

Such a query statement can only use a similar composite index:

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

5. Combined Index

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

The index scan can be used even when querying, in contrast to the defined sort.

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

}

Indexing in MongoDB on documents embedded in a subdocument