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db.collection.createIndex()¶
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Definition¶
- db.collection.createIndex(keys, options)¶
Creates indexes on collections.
Changed in version 3.2: Starting in MongoDB 3.2, MongoDB disallows the creation of version 0 indexes. To upgrade existing version 0 indexes, see Version 0 Indexes.
Parameter Type Description keys document A document that contains the field and value pairs where the field is the index key and the value describes the type of index for that field. For an ascending index on a field, specify a value of 1; for descending index, specify a value of -1.
MongoDB supports several different index types including text, geospatial, and hashed indexes. See Index Types for more information.
options document Optional. A document that contains a set of options that controls the creation of the index. See Options for details.
Options¶
The options document contains a set of options that controls the creation of the index. Different index types can have additional options specific for that type.
Options for All Index Types¶
The following options are available for all index types unless otherwise specified:
Changed in version 3.0: The dropDups option is no longer available.
| Parameter | Type | Description |
|---|---|---|
| background | boolean | Optional. Builds the index in the background so that building an index does not block other database activities. Specify true to build in the background. The default value is false. |
| unique | boolean | Optional. Creates a unique index so that the collection will not accept insertion of documents where the index key or keys match an existing value in the index. Specify true to create a unique index. The default value is false. The option is unavailable for hashed indexes. |
| name | string | Optional. The name of the index. If unspecified, MongoDB generates an index name by concatenating the names of the indexed fields and the sort order. Whether user specified or MongoDB generated, index names including their full namespace (i.e. database.collection) cannot be longer than the Index Name Limit. |
| partialFilterExpression | document | Optional. If specified, the index only references documents that match the filter expression. See Partial Indexes for more information. A filter expression can include:
You can specify a partialFilterExpression option for all MongoDB index types. New in version 3.2. |
| sparse | boolean | Optional. If true, the index only references documents with the specified field. These indexes use less space but behave differently in some situations (particularly sorts). The default value is false. See Sparse Indexes for more information. Changed in version 3.2: Starting in MongoDB 3.2, MongoDB provides the option to create partial indexes. Partial indexes offer a superset of the functionality of sparse indexes. If you are using MongoDB 3.2 or later, partial indexes should be preferred over sparse indexes. Changed in version 2.6: 2dsphere indexes are sparse by default and ignore this option. For a compound index that includes 2dsphere index key(s) along with keys of other types, only the 2dsphere index fields determine whether the index references a document. 2d, geoHaystack, and text indexes behave similarly to the 2dsphere indexes. |
| expireAfterSeconds | integer | Optional. Specifies a value, in seconds, as a TTL to control how long MongoDB retains documents in this collection. See Expire Data from Collections by Setting TTL for more information on this functionality. This applies only to TTL indexes. |
| storageEngine | document | Optional. Allows users to specify configuration to the storage engine on a per-index basis when creating an index. The value of the storageEngine option should take the following form: { <storage-engine-name>: <options> }
Storage engine configuration specified when creating indexes are validated and logged to the oplog during replication to support replica sets with members that use different storage engines. New in version 3.0. |
Options for text Indexes¶
The following options are available for text indexes only:
| Parameter | Type | Description |
|---|---|---|
| weights | document | Optional. For text indexes, a document that contains field and weight pairs. The weight is an integer ranging from 1 to 99,999 and denotes the significance of the field relative to the other indexed fields in terms of the score. You can specify weights for some or all the indexed fields. See Control Search Results with Weights to adjust the scores. The default value is 1. |
| default_language | string | Optional. For text indexes, the language that determines the list of stop words and the rules for the stemmer and tokenizer. See Text Search Languages for the available languages and Specify a Language for Text Index for more information and examples. The default value is english. |
| language_override | string | Optional. For text indexes, the name of the field, in the collection’s documents, that contains the override language for the document. The default value is language. See Use any Field to Specify the Language for a Document for an example. |
| textIndexVersion | integer | Optional. For text indexes, the text index version number. Version can be either 1 or 2. In MongoDB 2.6, the default version is 2. MongoDB 2.4 can only support version 1. New in version 2.6. |
Options for 2dsphere Indexes¶
The following option is available for 2dsphere indexes only:
| Parameter | Type | Description |
|---|---|---|
| 2dsphereIndexVersion | integer | Optional. For 2dsphere indexes, the 2dsphere index version number. Version can be either 1 or 2. In MongoDB 2.6, the default version is 2. MongoDB 2.4 can only support version 1. New in version 2.6. |
Options for 2d Indexes¶
The following options are available for 2d indexes only:
| Parameter | Type | Description |
|---|---|---|
| bits | integer | Optional. For 2d indexes, the number of precision of the stored geohash value of the location data. The bits value ranges from 1 to 32 inclusive. The default value is 26. |
| min | number | Optional. For 2d indexes, the lower inclusive boundary for the longitude and latitude values. The default value is -180.0. |
| max | number | Optional. For 2d indexes, the upper inclusive boundary for the longitude and latitude values. The default value is 180.0. |
Options for geoHaystack Indexes¶
The following option is available for geoHaystack indexes only:
| Parameter | Type | Description |
|---|---|---|
| bucketSize | number | For geoHaystack indexes, specify the number of units within which to group the location values; i.e. group in the same bucket those location values that are within the specified number of units to each other. The value must be greater than 0. |
Behaviors¶
The createIndex() method has the behaviors described here.
To add or change index options you must drop the index using the dropIndex() method and issue another createIndex() operation with the new options.
If you create an index with one set of options, and then issue the createIndex() method with the same index fields and different options without first dropping the index, createIndex() will not rebuild the existing index with the new options.
If you call multiple createIndex() methods with the same index specification at the same time, only the first operation will succeed, all other operations will have no effect.
Non-background indexing operations will block all other operations on a database.
MongoDB will not create an index on a collection if the index entry for an existing document exceeds the Maximum Index Key Length. Previous versions of MongoDB would create the index but not index such documents.
Changed in version 2.6.
Examples¶
Create an Ascending Index on a Single Field¶
The following example creates an ascending index on the field orderDate.
db.collection.createIndex( { orderDate: 1 } )
If the keys document specifies more than one field, then createIndex() creates a compound index.
Create an Index on a Multiple Fields¶
The following example creates a compound index on the orderDate field (in ascending order) and the zipcode field (in descending order.)
db.collection.createIndex( { orderDate: 1, zipcode: -1 } )
A compound index cannot include a hashed index component.
Note
The order of an index is important for supporting sort() operations using the index.
Additional Information¶
- Use db.collection.createIndex() rather than db.collection.ensureIndex() to create indexes.
- The Indexes section of this manual for full documentation of indexes and indexing in MongoDB.
- db.collection.getIndexes() to view the specifications of existing indexes for a collection.
- Text Indexes for details on creating text indexes.
- Geospatial Indexes and geoHaystack Indexes for geospatial queries.
- TTL Indexes for expiration of data.
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