What is the role of sort predicates in indexes?

Sort predicates play a crucial role in defining the order in which query results are returned. When a query includes sorting criteria, MongoDB can utilize indexes to directly access the data in the desired order. This optimization can significantly enhance performance because it allows the database to retrieve results in the correct sequence without having to sort them in-memory after retrieval.

By leveraging sort predicates in conjunction with appropriate indexes, MongoDB minimizes the processing overhead typically associated with sorting large datasets. It also helps in reducing memory consumption, as sorting operations can be resource-intensive, particularly with large datasets. Therefore, the primary function of sort predicates in indexes is not only to determine how data is arranged in the output but also to streamline the query execution process by avoiding unnecessary sorting operations post-retrieval.