> For the complete MongoDB documentation index, see www.mongodb.com/docs/llms.txt # Create an Index If your application repeatedly runs queries on the same fields, create an index on those fields to improve performance. To create an index, use the [`createIndex()`](https://www.mongodb.com/docs/manual/reference/method/db.collection.createindex.md#mongodb-method-db.collection.createIndex) shell method or equivalent method for your driver. This page shows examples for the MongoDB Shell and drivers. ## About this Task When you run a create index command in the MongoDB Shell or a driver, MongoDB only creates the index if an index of the same specification does not exist. Although indexes improve query performance, adding an index has negative performance impact for write operations. For collections with a high write-to-read ratio, indexes are expensive because each insert and update must also update any indexes. **Warning:** Do not create indexes on encrypted fields. Creating indexes on encrypted fields that use Queryable Encryption negatively affect performance. Instead, you can create an index on the `__safeContent__` field to support queries on encrypted fields. ## Procedure To create an index in [`mongosh`](https://www.mongodb.com/docs/mongodb-shell.md#mongodb-binary-bin.mongosh), use [`db.collection.createIndex()`.](https://www.mongodb.com/docs/manual/reference/method/db.collection.createindex.md#mongodb-method-db.collection.createIndex) ```javascript db.collection.createIndex( , ) ``` To create an index using the [Python driver](https://www.mongodb.com/docs/languages/python/pymongo-driver/current/), use the [pymongo.collection.Collection.create\_index](https://www.mongodb.com/docs/languages/python/pymongo-driver/current/work-with-indexes/#create-an-index) method: ```python db.collection.create_index([()], ) ``` To create an index using the [Motor driver](https://motor.readthedocs.io/en/stable/), use [`motor.motor_asyncio.AsyncIOMotorCollection.create_index`.](https://motor.readthedocs.io/en/stable/api-asyncio/asyncio_motor_collection.html#motor.motor_asyncio.AsyncIOMotorCollection.create_index) ```python await db.collection.create_index([()], ) ``` To create an index using the [Java driver](https://mongodb.github.io/mongo-java-driver/), use [com.mongodb.client.MongoCollection.createIndex](http://mongodb.github.io/mongo-java-driver/3.4/javadoc/?com/mongodb/client/MongoCollection.html#createIndex-org.bson.conversions.Bson-). ```java collection.createIndex(, ) ``` To create an index using the [Async Java driver](http://mongodb.github.io/mongo-java-driver/3.0/driver-async/), use [com.mongodb.async.client.MongoCollection.createIndex](http://mongodb.github.io/mongo-java-driver/3.4/javadoc/?com/mongodb/async/client/MongoCollection.html#createIndex-org.bson.conversions.Bson-com.mongodb.async.SingleResultCallback-). ```java collection.createIndex( , , ) ``` To create an index by using the [Kotlin Coroutine Driver](https://www.mongodb.com/docs/drivers/kotlin/coroutine/current/), use the [MongoCollection.createIndex()](https://mongodb.github.io/mongo-java-driver/5.11/apidocs/driver-kotlin-coroutine/mongodb-driver-kotlin-coroutine/com.mongodb.kotlin.client.coroutine/-mongo-collection/create-index.html) method. ```kotlin collection.createIndex(, ) ``` To create an index using the [Node.JS driver](https://www.mongodb.com/docs/drivers/node/current/), use `createIndex()`. ```javascript collection.createIndex( { }, function(err, result) { console.log(result); callback(result); } ) ``` To create an index using the [PHP driver](https://www.mongodb.com/docs/php-library/current/), use [`MongoDB\\Collection::createIndex()`.](https://www.mongodb.com/docs/php-library/upcoming/reference/method/MongoDBCollection-createIndex.md#mongodb-phpmethod-phpmethod.MongoDB-Collection--createIndex--) ```php $collection->createIndex(, ); ``` To create an index using the [Ruby driver](https://www.mongodb.com/docs/ruby-driver/current/), use [Mongo::Index::View#create\_one](http://www.rubydoc.info/github/mongodb/mongo-ruby-driver/Mongo%2FIndex%2FView%3Acreate_one). ```ruby client[:collection].indexes.create_one({ }, {options}) ``` To create an index using the [Scala driver](http://mongodb.github.io/mongo-scala-driver/), use [org.mongodb.scala.model.Indexes](https://mongodb.github.io/mongo-scala-driver/1.0/scaladoc/index.html#org.mongodb.scala.model.Indexes$). ```scala collection.createIndex() ``` To create an index using the [.NET driver](http://mongodb.github.io/mongo-csharp-driver/), use [MongoCollection.CreateIndex](http://api.mongodb.com/csharp/current/html/Overload_MongoDB_Driver_MongoCollection_CreateIndex.htm). ```csharp collection.CreateIndex( IndexKeys., ); ``` ## Example This example creates a single key ascending index on the `name` field: ```javascript db.collection.createIndex( { name: 1 } ) ``` This example creates a single key ascending index on the `name` field: ```python collection.create_index([("name", pymongo.ASCENDING)]) ``` This example creates a single key ascending index on the `name` field: ```python await collection.create_index([("name", pymongo.ASCENDING)]) ``` This example creates a single key ascending index on the `name` field: ```java collection.createIndex(Indexes.ascending("name")); ``` This example creates a single key ascending index on the `name` field: ```java collection.createIndex(Indexes.ascending("name"), someCallbackFunction()); ``` This example creates a single key ascending index on the `name` field: ```kotlin collection.createIndex(Indexes.descending("name")) ``` This example creates a single key ascending index on the `name` field: ```javascript collection.createIndex( { name : 1 }, function(err, result) { console.log(result); callback(result); } ) ``` This example creates a single key ascending index on the `name` field: ```php $collection->createIndex(['name' => 1]); ``` This example creates a single key ascending index on the `name` field: ```ruby client[:collection].indexes.create_one({ name: 1 }) ``` This example creates a single key ascending index on the `name` field: ```scala collection.createIndex(ascending("name")) ``` This example creates a single key ascending index on the `name` field: ```csharp collection.CreateIndex( IndexKeys.Ascending("name") ); ``` ## Results Use [`mongosh`](https://www.mongodb.com/docs/mongodb-shell.md#mongodb-binary-bin.mongosh) to monitor index creation. To see what indexes exist on your collection, including indexes that are currently being built, run the [`db.collection.getIndexes()`](https://www.mongodb.com/docs/manual/reference/method/db.collection.getindexes.md#mongodb-method-db.collection.getIndexes) method: ```javascript db.collection.getIndexes() ``` **Output:** ```javascript [ { v: 2, key: { _id: 1 }, name: '_id_' }, { v: 2, key: { name: -1 }, name: 'name_-1' } ] ``` To check whether your index is building, use [`$currentOp`](https://www.mongodb.com/docs/manual/reference/operator/aggregation/currentop.md#mongodb-pipeline-pipe.-currentOp) with [`db.aggregate()`](https://www.mongodb.com/docs/manual/reference/method/db.aggregate.md#mongodb-method-db.aggregate) on the `admin` database. The following aggregation pipeline uses the [`$match`](https://www.mongodb.com/docs/manual/reference/operator/aggregation/match.md#mongodb-pipeline-pipe.-match) stage to show an active operation building a descending index on the `name` field: ```javascript db.getSiblingDB("admin").aggregate( [ { $currentOp : { idleConnections: true } }, { $match : {"command.createIndexes": { $exists: true } } } ] ) ``` **Output:** ```javascript [ { type: 'op', host: 'mongodb.example.net:27017', desc: 'conn584', connectionId: 584, client: '104.30.134.189:12077', appName: 'mongosh 2.3.4', clientMetadata: { ... }, active: true, currentOpTime: '2024-12-05T16:13:35.571+00:00', effectiveUsers: [ { user: jane-doe, db: 'admin' } ], isFromUserConnection: true, threaded: true, opid: ..., lsid: { ... }, secs_running: Long('3'), microsecs_running: Long('3920881'), op: 'command', ns: 'example_db.collection', redacted: false, command: { createIndexes: 'collection', indexes: [ { name: 'name_-1', key: { name: -1 } } ], apiVersion: '1', lsid: { id: UUID('570931be-c692-4963-b9e2-1e279efd9702') }, '$clusterTime': { clusterTime: Timestamp({ t: 1733415063, i: 32 }), signature: { hash: Binary.createFromBase64('z0zaUHJ5SfhNQyvQLhocsKRFNbo=', 0), keyId: Long('7444956895695077380') } }, '$db': 'example_db' }, numYields: 0, queues: { ... }, currentQueue: null, locks: {}, waitingForLock: false, lockStats: { ... }, waitingForFlowControl: false, flowControlStats: { acquireCount: Long('3') } }, ... ] ``` MongoDB marks index builds in various stages, including waiting on commit quorum, as an idle connection by setting the `active` field to `false`. The `idleConnections: true` setting includes these idle connections in the `$currentOp` output. To view information on existing indexes using a driver, refer to your [driver's documentation.](https://www.mongodb.com/docs/drivers/) ## Learn More - To learn how to create indexes in MongoDB Compass, see [Manage Indexes](https://www.mongodb.com/docs/compass/current/indexes.md#std-label-compass-indexes) in the Compass documentation. - To see how often your indexes are used, see [Measure Index Use.](https://www.mongodb.com/docs/manual/tutorial/measure-index-use.md#std-label-index-measure-index-use) - To learn how to specify the name of your index, see [Specify an Index Name.](https://www.mongodb.com/docs/manual/core/indexes/create-index/specify-index-name.md#std-label-specify-index-name) - To learn how MongoDB builds indexes, see [Index Build Process.](https://www.mongodb.com/docs/manual/core/index-creation.md#std-label-index-build-process)