What is the function of equality predicates in indexes?

The function of equality predicates in indexes is to test for exact matches on a single field. When a query utilizes an equality predicate, it looks for documents that have a specific value in a given field. This characteristic makes it highly efficient because the index can quickly pinpoint the location of documents that match the specified value, rather than scanning through all documents in a collection.

Indexes are structured to optimize searches, and when an equality predicate is applied, the database can utilize these indexes to improve performance significantly. By indexing fields that are commonly queried with equality checks, MongoDB can retrieve results faster, which is especially beneficial for larger datasets where a full collection scan would be impractical and time-consuming.

The other options address different functionalities or concepts related to indexing and querying. For example, approximate matches pertain to different types of predicates, such as range queries, while sorting capabilities relate to order rather than exact matches. Managing index storage efficiency also doesn’t directly relate to the uniqueness of equality predicates, but rather to how data is structured within indexes for optimal use.