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Modify Query Results

Overview

In this guide, you can learn how to sort, skip, and limit the results of a query by using the MongoDB Extension for Hibernate ORM.

Sort Results

You can sort query results by the value of a specified field by using the order by clause in your query statement. By default, the order by clause sorts documents in ascending order. To sort documents in descending order, append the desc keyword to the field name.

The following example retrieves matching documents from the sample_mflix.movies collection and sorts them by the year field in descending order:

var sortResult = session.createQuery("from Movie where title = :t order by year desc", Movie.class)
                        .setParameter("t", "Cinderella")
                        .getResultList();
for (var m : sortResult) {
    System.out.println("Title: " + m.getTitle() + ", Year: " + m.getYear());
}

Title: Cinderella, Year: 2015
Title: Cinderella, Year: 1997
Title: Cinderella, Year: 1950

var sortResult = entityManager.createQuery("select m from Movie m where m.title = :t order by m.year desc", Movie.class)
                              .setParameter("t", "Cinderella")
                              .getResultList();
for (var m : sortResult) {
    System.out.println("Title: " + m.getTitle() + ", Year: " + m.getYear());
}

Title: Cinderella, Year: 2015
Title: Cinderella, Year: 1997
Title: Cinderella, Year: 1950

Skip Results

You can skip a specified number of documents in your query results by chaining the setFirstResult() method to the query. Pass the number of initial documents to skip as an argument to this method.

The following example runs the same query as the preceding example but skips the first matching document in the results:

var skipResult = session.createQuery("from Movie where title = :t order by year desc", Movie.class)
                        .setParameter("t", "Cinderella")
                        .setFirstResult(1)
                        .getResultList();
for (var m : skipResult) {
    System.out.println("Title: " + m.getTitle() + ", Year: " + m.getYear());
}

Title: Cinderella, Year: 1997
Title: Cinderella, Year: 1950

var skipResult = entityManager.createQuery("select m from Movie m where m.title = :t order by m.year desc", Movie.class)
                              .setParameter("t", "Cinderella")
                              .setFirstResult(1)
                              .getResultList();
for (var m : skipResult) {
    System.out.println("Title: " + m.getTitle() + ", Year: " + m.getYear());
}

Title: Cinderella, Year: 1997
Title: Cinderella, Year: 1950

Limit Results

You can limit the number of documents that your query returns by chaining the setMaxResults() method to the query. Pass the maximum number of documents to return as an argument to this method.

The following example runs the same query as the sort example but returns up to two matching documents in the results:

var limitResult = session.createQuery("from Movie where title = :t order by year desc", Movie.class)
                         .setParameter("t", "Cinderella")
                         .setMaxResults(2)
                         .getResultList();
for (var m : limitResult) {
    System.out.println("Title: " + m.getTitle() + ", Year: " + m.getYear());
}

Title: Cinderella, Year: 2015
Title: Cinderella, Year: 1997

var limitResult = entityManager.createQuery("select m from Movie m where m.title = :t order by m.year desc", Movie.class)
                               .setParameter("t", "Cinderella")
                               .setMaxResults(2)
                               .getResultList();
for (var m : limitResult) {
    System.out.println("Title: " + m.getTitle() + ", Year: " + m.getYear());
}

Title: Cinderella, Year: 2015
Title: Cinderella, Year: 1997

Alternatively, you can use a limit clause in your HQL or JPQL statement to restrict the number of documents that your query returns, as shown in the following code:

var limitClauseResult = session.createQuery("from Movie where title = :t order by year desc limit 2", Movie.class)
                               .setParameter("t", "Cinderella")
                               .getResultList();

var limitClauseResult = entityManager.createQuery("select m from Movie m where m.title = :t order by m.year desc limit 2", Movie.class)
                                     .setParameter("t", "Cinderella")
                                     .getResultList();

Additional Information

To learn more about performing other operations on your MongoDB data, see the Perform CRUD Operations guide.

To learn more about using HQL and JPQL to run queries, see A Guide to Hibernate Query Language in the Hibernate ORM documentation.

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