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= createIndex() =
----
[[MongoDB Driver Function Reference]]


Creates an index on the collection.
More information can be found in the corresponding entry of the [[https://docs.mongodb.com/manual/reference/method/db.collection.createIndex/index.html|MongoDB Manual]].


[[[@cG

<collection>.createIndex([<name>, ]<keys>[, <options>[, <commitQuorum>]])

]]]


**Arguments**

[[[@w

|@t0@r0@c0 <collection> | | The target collection. |
| <name> | | Index name |
| <keys> | | A BSON document specifying the index keys. |
| <options> | | A BOSN document specifying options. |
| <commitQuorum> | | A string or integer specifying the commit quorum. |

]]]


**Options**

[[[@cw

{ unique: <boolean>, name: <string>, sparse: <boolean>, expireAfterSeconds: <long>, storageEngine: <document> }
<<@f:text>>
|@t0@r0@c0 unique | | Creates a unique index. |
| name| | Provides an index name. |
| sparse | | Index will only reference documents with the specified key. |
| expireAfterSeconds| | Index expiration time. |
| storageEngine | | Storage engine definition. |
<<@/f>>
]]]



**Example**

[[[@cw

db.employees.createIndex("salary_ix", { salary: 1 });

]]]

Creates an index for the //salary// key on the //employees// collection.



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