Single Field Indexes

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Overview

Sample Data
Create Single Field Index
Additional Information
API Documentation

Overview

Single field indexes are indexes with a reference to a single field within a collection's documents. They improve single field query and sort performance, and support TTL Indexes that automatically remove documents from a collection after a certain amount of time or at a specific clock time.

When creating a single field index, you must specify the following:

The field on which to create the index
The sort order for the indexed values (ascending or descending)

Note

The _id_ index is an example of a single field index. This index is automatically created on the _id field when a new collection is created.

Sample Data

The examples in this guide use the movies collection in the sample_mflix database from the Atlas sample datasets. To learn how to create a free MongoDB Atlas cluster and load the sample datasets, see the Get Started with Atlas guide.

The following Kotlin data class models the documents in this collection:

data class Movie(
    @BsonId
    val id: ObjectId,
    val title: String? = "",
    val type: String? = "",
    val genres: List<String>? = null,
    val cast: List<String>? = null,
    val plot: String? = "",
)

Create Single Field Index

The following example creates an index in ascending order on the title field:

collection.createIndex(Indexes.ascending(Movie::title.name))

The following is an example of a query that is covered by the index created in the preceding code example:

val filter = Filters.eq(Movie::title.name, "Batman")
val sort = Sorts.ascending(Movie::title.name)
val results = collection.find(filter).sort(sort)
results.forEach { result ->
    println(result)
}

Movie(id=573a1398f29313caabceb515, title=Batman, ...)

Additional Information

To learn more about single field indexes, see Single Field Indexes in the MongoDB Server manual.

API Documentation

To learn more about any of the methods discussed in this guide, see the following API documentation:

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Work with Indexes

Compound