Compound Indexes

Overview

Compound indexes hold references to multiple fields within a collection's documents, improving query and sort performance.

When creating a compound index, you must specify the following:

• The fields on which to create the index

• The sort order for each field (ascending or descending)

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 a Compound Index

The following example creates a compound index on the type and genre fields, with both fields indexed in ascending order:

collection.createIndex(Indexes.ascending(Movie::type.name, Movie::genres.name))

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

val filter = and(
    eq(Movie::type.name, "movie"),
    `in`(Movie::genres.name, "Drama")
)
val sort = Sorts.ascending(Movie::type.name, Movie::genres.name)
val results = collection.find(filter).sort(sort)
results.forEach { result ->
    println(result)
}

Additional Information

To learn more about compound indexes, see Compound Indexes in the MongoDB Server manual.

To learn about effective indexing strategies using compound indexes, see The ESR Rule in the MongoDB Server manual.