Index management for MongoDB learning Note 22 MongoDB

Use the Ensureindex function to create an index of the collection.

For collections, each index needs to be created once, and duplicate creation has no effect;

> Show Collections System.indexes Users

The index metadata of all the databases is stored in the System.indexs collection;

Use the Getindexes function to view index information on a given collection:

> db.users.getindexes ()    [        {              "V"  : 1,              "Key"  : {                  "_id"  : 1             },             "Name"  :  "_id_",             "ns"  :   "Blog.users"         },         {             "V"  : 1,              "Key"  : {                  "username"  : 1             },             "Name"  :  "Username_1",             "ns"  :   "Blog.users"         },         {             "V"  : 1,              "Key"  : {                  "Age"  : 1,                  "username"  : 1             },              "name"  :  "Age_1_username_1",              "ns"  :  "Blog.users"         }     ]    >

The

can accommodate the Dropindex function to delete the specified index:

> db.users.dropindex ({"username": 1})    {  "Nindexeswas"  : 3,  "OK"  : 1 }    > db.users.getindexes ()     [         {              "V"  : 1,             "key"  :  {                 "_id"  : 1            },              "name"  :  "_id_",              "ns"  :  "Blog.users"          },        {              "V" : 1,             "Key"  : {                  "Age"  :  1,                 " Username " : 1            },              "name"  :  "Age_1_username_1",              "ns"  :  "Blog.users"          }    ]    >

In the example above, you can see that the index's identity default format is Keyname1_dir1_keyname2_dir....keynamen_dirn;

You can also specify an identity name:

> db.users.ensureindex ({"username": 1},{"name": "FirstName"})    {          "Createdcollectionautomatically"  : false,          "Numindexesbefore"  : 2,         " Numindexesafter " : 3,        " OK " : 1     }    > db.users.getindexes ()     [         {             " V " : 1,            " key " : {                  "_id"  :  1            },              "name"  :  "_id_",             "ns"  :  "Blog.users"         },         {             "V"  : 1,              "Key"  : {                  "Age"  : 1,                  "username"  : 1             },              "name"  :  "Age_1_username_1",              "ns"  :  "Blog.users"          },        {             "V"  : 1,             "Key"  : {                  "username"  : 1            },              "Name"  :  "FirstName",              "ns"  :  "Blog.users"          }    ]    >

To modify an index: Delete index, CREATE index;

Dropping an index allows you to specify the index identity directly, for example:

> db.users.dropindex ("FirstName")    {  "Nindexeswas"  : 3,  "OK"   :  1 }    > db.users.getindexes ()     [         {             " V " : 1,            " key " : {                  "_id"  :  1            },              "name"  :  "_id_",              "ns"  :  "Blog.users"          },        {              "V"  : 1,             "Key"  : {                  "Age"  : 1,                  "username"  : 1            },              "name"  :  "Age_1_username_1",              "ns"  :  "Blog.users"          }    ]    >

This article is from the "Margin with Wish" blog, please be sure to keep this source http://281816327.blog.51cto.com/907015/1600882

Index management for MongoDB learning Note 22 MongoDB