Development: Avoid database queries with pagination and left join fetch

docs/dev/guidelines/database.rst

@@ -155,7 +155,7 @@ In order to load the relationships of an entity on demand, we then use one of 3
     @EntityGraph(type = LOAD, attributePaths = { "exercises", "exercises.categories", "exercises.teamAssignmentConfig" })
     Course findWithEagerExercisesById(long courseId);
 
-2. **JOIN FETCH**: The ``JOIN FETCH`` keyword is used in a custom query to specify a graph of relationships to fetch. It should be used when a query is custom and has a custom ``@Query`` annotation. Example:
+2. **JOIN FETCH**: The ``JOIN FETCH`` keyword is used in a custom query to specify a graph of relationships to fetch. It should be used when a query is custom and has a custom ``@Query`` annotation. You can see the example below. Also, explicitly or implicitly limiting queries in Hibernate can lead to in-memory paging. For more details, see the 'In-memory paging' section.
 
  .. code-block:: java
 
@@ -204,6 +204,73 @@ In order to load the relationships of an entity on demand, we then use one of 3
     final Set<ProgrammingExerciseFetchOptions> fetchOptions = withGradingCriteria ? Set.of(GradingCriteria, AuxiliaryRepositories) : Set.of(AuxiliaryRepositories);
     var programmingExercise = programmingExerciseRepository.findByIdWithDynamicFetchElseThrow(exerciseId, fetchOptions);
 
+4. **In memory paging**: Since the flag ``hibernate.query.fail_on_pagination_over_collection_fetch: true`` is now active, it is crucial to carefully craft database queries that involve FETCH statements with collections and thoroughly test the changes. In-memory paging would cause performance decrements and is, therefore, disabled. Any use of it will lead to runtime errors.
+Queries that may result in this error can return Page<> and contain JOIN FETCHES or involve internal limiting in Hibernate, such as findFirst, findLast, or findOne. One solution is to split the original query into multiple queries and a default method. The first query fetches only the IDs of entities whose full dependencies need to be fetched. The second query eagerly fetches all necessary dependencies, and the third query uses counting to build Pages, if they are utilized.
+When possible, use the default Spring Data/JPA methods for second(fetching) and third(counting) queries.
+An example implementation could look like this:
+
+ .. code-block:: java
+
+    // Repository interface
+    default Page<User> searchAllByLoginOrNameInCourseAndReturnPage(Pageable pageable, String loginOrName, long courseId) {
+        List<Long> userIds = findUserIdsByLoginOrNameInCourse(loginOrName, courseId, pageable).stream().map(DomainObject::getId).toList();;
+
+        if (userIds.isEmpty()) {
+            return new PageImpl<>(Collections.emptyList(), pageable, 0);
+        }
+
+        List<User> users = findUsersWithGroupsByIds(userIds);
+        long total = countUsersByLoginOrNameInCourse(loginOrName, courseId);
+
+        return new PageImpl<>(users, pageable, total);
+    }
+
+    @Query("""
+            SELECT DISTINCT user
+            FROM User user
+                JOIN user.groups userGroup
+                JOIN Course course ON course.id = :courseId
+            WHERE user.isDeleted = FALSE
+                AND (
+                    user.login LIKE :#{#loginOrName}%
+                    OR CONCAT(user.firstName, ' ', user.lastName) LIKE %:#{#loginOrName}%
+                )
+                AND (course.studentGroupName = userGroup
+                    OR course.teachingAssistantGroupName = userGroup
+                    OR course.editorGroupName = userGroup
+                    OR course.instructorGroupName = userGroup
+                )
+            """)
+    List<User> findUsersByLoginOrNameInCourse(@Param("loginOrName") String loginOrName, @Param("courseId") long courseId, Pageable pageable);
+
+    @Query("""
+            SELECT DISTINCT user
+            FROM User user
+                LEFT JOIN FETCH user.groups userGroup
+            WHERE user.id IN :ids
+            """)
+    List<User> findUsersWithGroupsByIds(@Param("ids") List<Long> ids);
+
+    @Query("""
+            SELECT COUNT(DISTINCT user)
+            FROM User user
+                JOIN user.groups userGroup
+                JOIN Course course ON course.id = :courseId
+            WHERE user.isDeleted = FALSE
+                AND (
+                    user.login LIKE :#{#loginOrName}%
+                    OR CONCAT(user.firstName, ' ', user.lastName) LIKE %:#{#loginOrName}%
+                )
+                AND (
+                    course.studentGroupName = userGroup
+                    OR course.teachingAssistantGroupName = userGroup
+                    OR course.editorGroupName = userGroup
+                    OR course.instructorGroupName = userGroup
+                )
+            """)
+    long countUsersByLoginOrNameInCourse(@Param("loginOrName") String loginOrName, @Param("courseId") long courseId);
+
+
 
 
 Best Practices

src/main/java/de/tum/in/www1/artemis/repository/BuildJobRepository.java

@@ -1,6 +1,7 @@
 package de.tum.in.www1.artemis.repository;
 
 import static de.tum.in.www1.artemis.config.Constants.PROFILE_CORE;
+import static org.springframework.data.jpa.repository.EntityGraph.EntityGraphType.LOAD;
 
 import java.time.Duration;
 import java.time.ZonedDateTime;
@@ -10,6 +11,7 @@
 
 import org.springframework.context.annotation.Profile;
 import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.EntityGraph;
 import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
@@ -33,9 +35,29 @@ public interface BuildJobRepository extends ArtemisJpaRepository<BuildJob, Long>
 
     Optional<BuildJob> findBuildJobByResult(Result result);
 
-    // TODO: rewrite this query, pageable does not work well with EntityGraph
-    @EntityGraph(attributePaths = { "result", "result.participation", "result.participation.exercise", "result.submission" })
-    Page<BuildJob> findAll(Pageable pageable);
+    @Query("""
+            SELECT b.id
+            FROM BuildJob b
+            """)
+    List<Long> findAllIds(Pageable pageable);
+
+    @EntityGraph(type = LOAD, attributePaths = { "result", "result.participation", "result.participation.exercise", "result.submission" })
+    List<BuildJob> findWithDataByIdIn(List<Long> ids);
+
+    /**
+     * Retrieves a paginated list of all {@link BuildJob} entities.
+     *
+     * @param pageable the pagination information.
+     * @return a paginated list of {@link BuildJob} entities. If no entities are found, returns an empty page.
+     */
+    default Page<BuildJob> findAllWithData(Pageable pageable) {
+        List<Long> ids = findAllIds(pageable);
+        if (ids.isEmpty()) {
+            return Page.empty(pageable);
+        }
+        List<BuildJob> result = findWithDataByIdIn(ids);
+        return new PageImpl<>(result, pageable, count());
+    }
 
     // Cast to string is necessary. Otherwise, the query will fail on PostgreSQL.
     @Query("""
@@ -56,17 +78,6 @@ Page<Long> findAllByFilterCriteria(@Param("buildStatus") BuildStatus buildStatus
             @Param("startDate") ZonedDateTime startDate, @Param("endDate") ZonedDateTime endDate, @Param("searchTerm") String searchTerm, @Param("courseId") Long courseId,
             @Param("durationLower") Duration durationLower, @Param("durationUpper") Duration durationUpper, Pageable pageable);
 
-    @Query("""
-            SELECT b
-            FROM BuildJob b
-                LEFT JOIN FETCH b.result r
-                LEFT JOIN FETCH r.participation p
-                LEFT JOIN FETCH p.exercise
-                LEFT JOIN FETCH r.submission
-            WHERE b.id IN :buildJobIds
-            """)
-    List<BuildJob> findAllByIdWithResults(@Param("buildJobIds") List<Long> buildJobIds);
-
     @Query("""
             SELECT new de.tum.in.www1.artemis.service.connectors.localci.dto.DockerImageBuild(
                 b.dockerImage,
@@ -77,9 +88,30 @@ Page<Long> findAllByFilterCriteria(@Param("buildStatus") BuildStatus buildStatus
             """)
     Set<DockerImageBuild> findAllLastBuildDatesForDockerImages();
 
-    // TODO: rewrite this query, pageable does not work well with EntityGraph
-    @EntityGraph(attributePaths = { "result", "result.participation", "result.participation.exercise", "result.submission" })
-    Page<BuildJob> findAllByCourseId(long courseId, Pageable pageable);
+    @Query("""
+            SELECT b.id
+            FROM BuildJob b
+            WHERE b.courseId = :courseId
+            """)
+    List<Long> findIdsByCourseId(@Param("courseId") long courseId, Pageable pageable);
+
+    long countBuildJobByCourseId(long courseId);
+
+    /**
+     * Retrieves a paginated list of all {@link BuildJob} entities that have a given course id.
+     *
+     * @param courseId the course id.
+     * @param pageable the pagination information.
+     * @return a paginated list of {@link BuildJob} entities. If no entities are found, returns an empty page.
+     */
+    default Page<BuildJob> findAllWithDataByCourseId(long courseId, Pageable pageable) {
+        List<Long> ids = findIdsByCourseId(courseId, pageable);
+        if (ids.isEmpty()) {
+            return Page.empty(pageable);
+        }
+        List<BuildJob> result = findWithDataByIdIn(ids);
+        return new PageImpl<>(result, pageable, countBuildJobByCourseId(courseId));
+    }
 
     @Query("""
              SELECT new de.tum.in.www1.artemis.service.connectors.localci.dto.ResultBuildJob(

src/main/java/de/tum/in/www1/artemis/repository/PersistenceAuditEventRepository.java

@@ -9,8 +9,11 @@
 import jakarta.validation.constraints.NotNull;
 
 import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.EntityGraph;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 import de.tum.in.www1.artemis.domain.PersistentAuditEvent;
 import de.tum.in.www1.artemis.repository.base.ArtemisJpaRepository;
@@ -23,14 +26,55 @@ public interface PersistenceAuditEventRepository extends ArtemisJpaRepository<Pe
     @EntityGraph(type = LOAD, attributePaths = { "data" })
     List<PersistentAuditEvent> findByPrincipalAndAuditEventDateAfterAndAuditEventType(String principle, Instant after, String type);
 
-    @EntityGraph(type = LOAD, attributePaths = { "data" })
-    // TODO: rewrite this query, pageable does not work well with EntityGraph
-    Page<PersistentAuditEvent> findAllByAuditEventDateBetween(Instant fromDate, Instant toDate, Pageable pageable);
+    @Query("""
+            SELECT p.id
+            FROM PersistentAuditEvent p
+            WHERE p.auditEventDate BETWEEN :fromDate AND :toDate
+            """)
+    List<Long> findIdsByAuditEventDateBetween(@Param("fromDate") Instant fromDate, @Param("toDate") Instant toDate, Pageable pageable);
 
-    @NotNull
-    @EntityGraph(type = LOAD, attributePaths = { "data" })
-    // TODO: rewrite this query, pageable does not work well with EntityGraph
-    Page<PersistentAuditEvent> findAll(@NotNull Pageable pageable);
+    @EntityGraph(type = LOAD, attributePaths = "data")
+    List<PersistentAuditEvent> findWithDataByIdIn(List<Long> ids);
+
+    long countByAuditEventDateBetween(Instant fromDate, Instant toDate);
+
+    /**
+     * Retrieves a paginated list of {@link PersistentAuditEvent} entities that have an audit event date between the specified fromDate and toDate.
+     *
+     * @param fromDate the start date of the audit event date range (inclusive).
+     * @param toDate   the end date of the audit event date range (inclusive).
+     * @param pageable the pagination information.
+     * @return a paginated list of {@link PersistentAuditEvent} entities within the specified date range. If no entities are found, returns an empty page.
+     */
+    default Page<PersistentAuditEvent> findAllWithDataByAuditEventDateBetween(Instant fromDate, Instant toDate, Pageable pageable) {
+        List<Long> ids = findIdsByAuditEventDateBetween(fromDate, toDate, pageable);
+        if (ids.isEmpty()) {
+            return Page.empty(pageable);
+        }
+        List<PersistentAuditEvent> result = findWithDataByIdIn(ids);
+        return new PageImpl<>(result, pageable, countByAuditEventDateBetween(fromDate, toDate));
+    }
+
+    @Query("""
+            SELECT p.id
+            FROM PersistentAuditEvent p
+            """)
+    List<Long> findAllIds(Pageable pageable);
+
+    /**
+     * Retrieves a paginated list of {@link PersistentAuditEvent} entities.
+     *
+     * @param pageable the pagination information.
+     * @return a paginated list of {@link PersistentAuditEvent} entities. If no entities are found, returns an empty page.
+     */
+    default Page<PersistentAuditEvent> findAllWithData(@NotNull Pageable pageable) {
+        List<Long> ids = findAllIds(pageable);
+        if (ids.isEmpty()) {
+            return Page.empty(pageable);
+        }
+        List<PersistentAuditEvent> result = findWithDataByIdIn(ids);
+        return new PageImpl<>(result, pageable, count());
+    }
 
     @NotNull
     @EntityGraph(type = LOAD, attributePaths = { "data" })

src/main/java/de/tum/in/www1/artemis/repository/ProgrammingSubmissionRepository.java

@@ -3,12 +3,14 @@
 import static de.tum.in.www1.artemis.config.Constants.PROFILE_CORE;
 import static org.springframework.data.jpa.repository.EntityGraph.EntityGraphType.LOAD;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 
 import jakarta.validation.constraints.NotNull;
 
 import org.springframework.context.annotation.Profile;
+import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.EntityGraph;
 import org.springframework.data.jpa.repository.Query;
@@ -17,6 +19,7 @@
 
 import de.tum.in.www1.artemis.domain.ProgrammingSubmission;
 import de.tum.in.www1.artemis.repository.base.ArtemisJpaRepository;
+import de.tum.in.www1.artemis.service.dto.ProgrammingSubmissionIdAndSubmissionDateDTO;
 
 /**
  * Spring Data JPA repository for the ProgrammingSubmission entity.
@@ -44,36 +47,72 @@ default ProgrammingSubmission findFirstByParticipationIdAndCommitHashOrderByIdDe
         return findByParticipationIdAndCommitHashOrderByIdDescWithFeedbacksAndTeamStudents(participationId, commitHash).stream().findFirst().orElse(null);
     }
 
-    @EntityGraph(type = LOAD, attributePaths = "results")
-    Optional<ProgrammingSubmission> findFirstByParticipationIdOrderBySubmissionDateDesc(long participationId);
+    @Query(value = """
+            SELECT new de.tum.in.www1.artemis.service.dto.ProgrammingSubmissionIdAndSubmissionDateDTO(ps.id, ps.submissionDate)
+            FROM ProgrammingSubmission ps
+            WHERE ps.participation.id = :participationId ORDER BY ps.submissionDate DESC
+            """)
+    List<ProgrammingSubmissionIdAndSubmissionDateDTO> findFirstIdByParticipationIdOrderBySubmissionDateDesc(@Param("participationId") long participationId, Pageable pageable);
+
+    @EntityGraph(type = LOAD, attributePaths = { "results" })
+    Optional<ProgrammingSubmission> findProgrammingSubmissionWithResultsById(long programmingSubmissionId);
 
     /**
-     * Provide a list of graded submissions. To be graded a submission must:
-     * - be of type 'INSTRUCTOR' or 'TEST'
-     * - have a submission date before the exercise due date
-     * - or related to an exercise without a due date
+     * Finds the first programming submission by participation ID, including its results, ordered by submission date in descending order. To avoid in-memory paging by retrieving
+     * the first submission directly from the database.
      *
-     * @param participationId to which the submissions belong.
-     * @param pageable        Pageable
-     * @return ProgrammingSubmission list (can be empty!)
+     * @param programmingSubmissionId the ID of the participation to find the submission for
+     * @return an {@code Optional} containing the first {@code ProgrammingSubmission} with results, ordered by submission date in descending order,
+     *         or an empty {@code Optional} if no submission is found
      */
+    default Optional<ProgrammingSubmission> findFirstByParticipationIdWithResultsOrderBySubmissionDateDesc(long programmingSubmissionId) {
+        Pageable pageable = PageRequest.of(0, 1); // fetch the first row
+        // probably is not the prettiest variant, but we need a way to fetch the first row only, as sql limit does not work with JPQL, as the latter is SQL agnostic
+        List<ProgrammingSubmissionIdAndSubmissionDateDTO> result = findFirstIdByParticipationIdOrderBySubmissionDateDesc(programmingSubmissionId, pageable);
+        if (result.isEmpty()) {
+            return Optional.empty();
+        }
+        long id = result.getFirst().programmingSubmissionId();
+        return findProgrammingSubmissionWithResultsById(id);
+    }
+
     @Query("""
-            SELECT s
+            SELECT new de.tum.in.www1.artemis.service.dto.ProgrammingSubmissionIdAndSubmissionDateDTO(s.id, s.submissionDate)
             FROM ProgrammingSubmission s
-                LEFT JOIN s.participation p
-                LEFT JOIN p.exercise e
-                LEFT JOIN FETCH s.results r
+                JOIN s.participation p
+                JOIN p.exercise e
             WHERE p.id = :participationId
-                AND (
-                    s.type = de.tum.in.www1.artemis.domain.enumeration.SubmissionType.INSTRUCTOR
+                AND (s.type = de.tum.in.www1.artemis.domain.enumeration.SubmissionType.INSTRUCTOR
                     OR s.type = de.tum.in.www1.artemis.domain.enumeration.SubmissionType.TEST
                     OR e.dueDate IS NULL
-                    OR s.submissionDate <= e.dueDate
-                )
+                    OR s.submissionDate <= e.dueDate)
             ORDER BY s.submissionDate DESC
             """)
-    // TODO: rewrite this query, pageable does not work well with left join fetch, it needs to transfer all results and only page in java
-    List<ProgrammingSubmission> findGradedByParticipationIdOrderBySubmissionDateDesc(@Param("participationId") long participationId, Pageable pageable);
+    List<ProgrammingSubmissionIdAndSubmissionDateDTO> findSubmissionIdsAndDatesByParticipationId(@Param("participationId") long participationId, Pageable pageable);
+
+    @EntityGraph(type = LOAD, attributePaths = { "results" })
+    List<ProgrammingSubmission> findSubmissionsWithResultsByIdIn(List<Long> ids);
+
+    /**
+     * Provide a list of graded submissions. To be graded a submission must:
+     * - be of type 'INSTRUCTOR' or 'TEST'
+     * - have a submission date before the exercise due date
+     * - or related to an exercise without a due date
+     *
+     * @param participationId to which the submissions belong.
+     * @param pageable        Pageable
+     * @return ProgrammingSubmission list (can be empty!)
+     */
+    default List<ProgrammingSubmission> findGradedByParticipationIdWithResultsOrderBySubmissionDateDesc(long participationId, Pageable pageable) {
+        List<Long> ids = findSubmissionIdsAndDatesByParticipationId(participationId, pageable).stream().map(ProgrammingSubmissionIdAndSubmissionDateDTO::programmingSubmissionId)
+                .toList();
+
+        if (ids.isEmpty()) {
+            return Collections.emptyList();
+        }
+
+        return findSubmissionsWithResultsByIdIn(ids);
+    }
 
     @EntityGraph(type = LOAD, attributePaths = "results.feedbacks")
     Optional<ProgrammingSubmission> findWithEagerResultsAndFeedbacksById(long submissionId);