Spring Data JPA - Pagination

Table of Contents

Handling Pagination with Native Queries
- Custom Solutions for Pagination Challenges
Reading material

Handling Pagination with Native Queries

While native queries offer unparalleled flexibility in querying, they introduce specific challenges, particularly when combined with pagination and mapping results to custom DTOs or projection interfaces. Unlike JPQL, where Spring Data JPA automatically applies pagination, native queries require a more manual approach due to their direct interaction with the database, bypassing some JPA abstractions.

One effective strategy is to complement your native query with a countQuery. This approach involves specifying a separate SQL query to count the total number of rows that match your criteria, essential for accurate pagination. However, the effectiveness of this method can vary based on the database type and the version of Spring Data JPA, necessitating tailored solutions for different environments.

Implementing these strategies requires careful consideration of the specific requirements and constraints of your application, including the database system in use, performance implications, and the complexity of the queries involved.

Custom Solutions for Pagination Challenges

For developers facing these challenges, several strategies can be employed:

Manual Pagination Parameters

Incorporate pagination directly in your native SQL queries using LIMIT and OFFSET clauses, adjusting these based on the pagination information (page, size, etc.) calculated at the service layer.

// Repository Method with Manual Pagination Parameters
@Query(value = "SELECT * FROM users WHERE status = 'active' LIMIT :limit OFFSET :offset", nativeQuery = true)
List<User> findActiveUsersWithPagination(@Param("limit") int limit, @Param("offset") int offset);

Using a CountQuery for Pagination

This involves specifying a separate SQL query for counting the total number of entries, essential for implementing pagination.

You need to provide a count query that returns the total number of records included in the non-paged result. One way to do that is to provide the query String as the value of the countQuery attribute of the @Query annotation.

// Repository Method with CountQuery
@Query(value = "SELECT * FROM users WHERE department_id = :departmentId",
       countQuery = "SELECT count(*) FROM users WHERE department_id = :departmentId",
       nativeQuery = true)
Page<User> findByDepartmentIdWithPagination(@Param("departmentId") Long departmentId, Pageable pageable);

@Repository
public interface AuthorRepository extends CrudRepository<Author, Long>, PagingAndSortingRepository<Author, Long> {

    @Query(value="select * from author a where a.last_name= ?1",
            countQuery = "select count(id) from author a where a.last_name= ?1",
            nativeQuery = true)
    Page<Author> getAuthorsByLastName(String lastname, Pageable page);

    ...
}

If your repository method references a named native query, you need to provide the count query as a 2nd named query and add the suffix .count to its name.

@NamedNativeQuery(name = "Author.getAuthorsByLastName",
                    query = "select * from author a where a.last_name= ?1",
                    resultClass = Author.class)
@NamedNativeQuery(name = "Author.getAuthorsByLastName.count",
                    query = "select count(id) from author a where a.last_name= ?1")
@Entity
public class Author { ... }

Hybrid Approach

Utilize native queries for data retrieval with manual pagination and leverage JPQL for the count operation. This method benefits from the automatic pagination support in JPQL for counting while maintaining the flexibility of native queries for data fetching.

// Service Layer
public Page<User> findUsersByDepartment(Long departmentId, Pageable pageable) {
    List<User> users = userRepository.findUsersByDepartmentNative(departmentId, pageable.getPageSize(), pageable.getOffset());
    long count = userRepository.countUsersInDepartment(departmentId);

    return new PageImpl<>(users, pageable, count);
}

// Repository
@Query(value = "SELECT * FROM users WHERE department_id = :departmentId LIMIT :limit OFFSET :offset", nativeQuery = true)
List<User> findUsersByDepartmentNative(@Param("departmentId") Long departmentId, @Param("limit") int limit, @Param("offset") int offset);

@Query("SELECT count(u) FROM User u WHERE u.department.id = :departmentId")
long countUsersInDepartment(@Param("departmentId") Long departmentId);

Service Layer Pagination

Retrieve the necessary data using a native query (potentially fetching more data than required) and then perform pagination manually within the service layer, constructing a custom Page object to encapsulate the paginated result set.

// Assuming the native query fetches all active users
List<User> users = userRepository.findAllActiveUsers();
// Manual pagination logic applied in the service layer
List<User> paginatedUsers = users.stream().skip(page * size).limit(size).collect(Collectors.toList());
int total = users.size();
Page<User> userPage = new PageImpl<>(paginatedUsers, PageRequest.of(page, size), total);

Exploring Alternatives

For complex scenarios where native queries are preferred but pagination integration is cumbersome, consider using Criteria API or Querydsl. These provide a more flexible approach to constructing dynamic queries and might offer more seamless integration with Spring Data JPA’s pagination features.