Index a Field - Kotlin SDK

Indexes speed up some queries, but slow down inserts and updates. Realm Database stores indexes on disk, which makes your realm files larger. To index a field, use the @Index annotation:

class Movie: RealmObject {
    @Index
    val _id: Long = Random.nextLong()
    val starring: List<String> = listOf()
}

Indexes support the efficient execution of queries in Realm Database. Without indexes, Realm Database must perform a collection scan, i.e., scan every document in a collection, to select those documents that match a query. If an appropriate index exists for a query, Realm Database can use the index to limit the number of documents that it must inspect.

Indexes are special data structures that store a small portion of a realm's data in an easy to traverse form. The index stores the value of a specific field ordered by the value of the field. The ordering of the index entries supports efficient equality matches and range-based query operations.

You can index fields with the following types:

• String
• Byte
• Short
• Int
• Long
• Boolean
• RealmInstant