Make sure we first filter on assignment id

src/main/java/nl/tudelft/labracore/repository/SubmissionRepository.java

@@ -19,8 +19,8 @@ package nl.tudelft.labracore.repository;
 
 import static com.querydsl.jpa.JPAExpressions.select;
 
-import java.util.List;
-import java.util.Optional;
+import java.util.*;
+import java.util.stream.Collectors;
 
 import org.springframework.data.domain.Sort;
 import org.springframework.data.jpa.repository.JpaRepository;
@@ -99,14 +99,22 @@ public interface SubmissionRepository
 	 * @return              The list of Submissions.
 	 */
 	default List<Submission> findByAssignmentIdFiltered(Long assignmentId, String filter, Boolean isLatest) {
-		List<Submission> submissions = findAll(qs.group.name.likeIgnoreCase("%" + filter + "%")
+		List<Submission> submissions = findAll(qs.assignment.id.eq(assignmentId).and(qs.group.name
+				.likeIgnoreCase(
+						"%" + filter + "%")
 				.or(qs.submitter.id.in(
-						select(qcp.id).from(qcp).where(qcp.username.likeIgnoreCase("%" + filter + "%")))));
-		return isLatest
-				? submissions.stream().map(Submission::getGroup).distinct()
-						.map(g -> findLatestSubmissionForGroup(g.getId(), assignmentId))
-						.filter(Optional::isPresent).map(Optional::get).toList()
-				: submissions;
+						select(qcp.id).from(qcp).where(qcp.username.likeIgnoreCase("%" + filter + "%"))))));
+		if (isLatest) {
+			// Get the latest assignment per group.
+			return submissions.stream().collect(Collectors.groupingBy(Submission::getGroup)).entrySet()
+					.stream()
+					.collect(Collectors.toMap(Map.Entry::getKey,
+							(l) -> l.getValue().stream()
+									.max(Comparator.comparing(Submission::getSubmissionTime))))
+					.values().stream().map(Optional::get).toList();
+		} else {
+			return submissions;
+		}
 	}
 
 	/**