⚡️ perf: prefetch user profile authorities before returning seat generation algorithm results to reduce db round trips for each profile.authorities fetch operation

Author: ge85riz

backend/src/main/java/com/itestra/eep/repositories/EventRepository.java

@@ -37,35 +37,43 @@ public interface EventRepository extends JpaRepository<Event, UUID> {
     @Query("SELECT e FROM Event e WHERE e.id = :id")
     Optional<Event> findByIdWithUpdateLock(@Param("id") UUID id);
 
+    // since we are using SeatAllocationDetailsDTO's constructor,
+    // we cannot explicitly use @EntityGraph; therefore, we have to join profile.authorities.
     @Query("""
             SELECT new com.itestra.eep.dtos.SeatAllocationDetailsDTO(
-                p.employee.profile,
+                prof,
                 p.id,
                 CAST(null AS java.util.UUID),
                 p.chair.id,
                 CAST(null AS java.lang.String)
             )
             FROM Event e
             JOIN e.employeeParticipations p
+            JOIN p.employee emp
+            JOIN emp.profile prof
+            LEFT JOIN FETCH prof.authorities
             WHERE e.id = :eventId
             
             UNION
             
             SELECT new com.itestra.eep.dtos.SeatAllocationDetailsDTO(
-                v.profile,
+                prof,
                 v.id,
                 v.invitor.id,
                 v.chair.id,
                 v.accessLink
             )
             FROM Event e
             JOIN e.visitorParticipations v
+            JOIN v.profile prof
+            LEFT JOIN FETCH prof.authorities
             WHERE e.id = :eventId
             """)
     List<SeatAllocationDetailsDTO> findCurrentSeatAllocationsByEventId(@Param("eventId") UUID eventId);
 
 
-    @EntityGraph(attributePaths = {"employeeParticipations.employee.profile.authorities",
+    @EntityGraph(attributePaths = {
+            "employeeParticipations.employee.profile.authorities",
             "visitorParticipations.profile.authorities"})
     @Query("""
             SELECT p.employee.profile

backend/src/main/java/com/itestra/eep/repositories/custom/PreviousMatchesRepositoryCustom.java

@@ -8,6 +8,6 @@
 @Repository
 public interface PreviousMatchesRepositoryCustom {
 
-    void batchInsertPreviousMatches(List<PreviousMatch> matches);
+    void batchInsertPreviousMatches(List<PreviousMatch.PreviousMatchId> matches);
 
 }

backend/src/main/java/com/itestra/eep/repositories/custom/impl/PreviousMatchesRepositoryCustomImpl.java

@@ -16,7 +16,7 @@ public class PreviousMatchesRepositoryCustomImpl implements PreviousMatchesRepos
     private final JdbcTemplate jdbcTemplate;
 
     @Override
-    public void batchInsertPreviousMatches(List<PreviousMatch> matches) {
+    public void batchInsertPreviousMatches(List<PreviousMatch.PreviousMatchId> matches) {
         if (matches.isEmpty()) {
             return;
         }
@@ -29,10 +29,10 @@ public void batchInsertPreviousMatches(List<PreviousMatch> matches) {
                 """;
 
         jdbcTemplate.batchUpdate(sql, matches, matches.size(),
-                (PreparedStatement ps, PreviousMatch match) -> {
-                    ps.setObject(1, match.getId().getFirstEmployeeId());
-                    ps.setObject(2, match.getId().getSecondEmployeeId());
-                    ps.setObject(3, match.getId().getEventId());
+                (PreparedStatement ps, PreviousMatch.PreviousMatchId match) -> {
+                    ps.setObject(1, match.getFirstEmployeeId());
+                    ps.setObject(2, match.getSecondEmployeeId());
+                    ps.setObject(3, match.getEventId());
                 });
     }
 

backend/src/main/java/com/itestra/eep/services/impl/SeatAllocationServiceImpl.java

@@ -96,20 +96,20 @@ private void persistNewEmployeePreviousMatches(UUID eventId, UUID[] neighborProf
         }
 
         UUID employeeId = employeeParticipation.get().getEmployee().getId();
-        List<PreviousMatch> newPreviousMatches = calculateBidirectionalMatches(employeeId, neighborProfileIds, eventId);
+        List<PreviousMatch.PreviousMatchId> newPreviousMatches = calculateBidirectionalMatches(employeeId, neighborProfileIds, eventId);
 
         if (!newPreviousMatches.isEmpty()) {
             previousMatchesRepository.batchInsertPreviousMatches(newPreviousMatches);
         }
     }
 
-    private List<PreviousMatch> calculateBidirectionalMatches(UUID employeeId, UUID[] neighborIds, UUID eventId) {
-        List<PreviousMatch> matches = new ArrayList<>(neighborIds.length * 2);
+    private List<PreviousMatch.PreviousMatchId> calculateBidirectionalMatches(UUID employeeId, UUID[] neighborIds, UUID eventId) {
+        List<PreviousMatch.PreviousMatchId> matches = new ArrayList<>(neighborIds.length * 2);
 
         for (UUID neighborId : neighborIds) {
             // we create bidirectional matches here
-            matches.add(new PreviousMatch(new PreviousMatch.PreviousMatchId(employeeId, neighborId, eventId)));
-            matches.add(new PreviousMatch(new PreviousMatch.PreviousMatchId(neighborId, employeeId, eventId)));
+            matches.add(new PreviousMatch.PreviousMatchId(employeeId, neighborId, eventId));
+            matches.add(new PreviousMatch.PreviousMatchId(neighborId, employeeId, eventId));
         }
 
         return matches;
@@ -118,6 +118,12 @@ private List<PreviousMatch> calculateBidirectionalMatches(UUID employeeId, UUID[
 
     @Override
     public void performTableBasedSeatAllocation(UUID eventId, StageMapDTO stageMap) throws IOException, InterruptedException {
+
+        // Delete all previous matches for this event before we start calculating for a clean state
+        // in case of any exception, they will be rolled back of course.
+        previousMatchesRepository.deleteAllByEventId(eventId);
+        previousMatchesRepository.flush();
+
         Event event = eventRepository.findByIdJoinedWithPreviousMatches(eventId).orElseThrow(EventNotFoundException::new);
 
         List<EmployeeParticipation> employeeParticipations = event.getEmployeeParticipations().stream().toList();
@@ -224,20 +230,18 @@ private void persistNewChairAssignments(UUID eventId, List<Chair> chairsToPersis
     }
 
     private void persistPreviousMatchesDueToNewMatchings(UUID eventId, Map<UUID, List<UUID>> tableToEmployeesMap) {
-        // Delete all previous matches for this event
-        previousMatchesRepository.deleteAllByEventId(eventId);
 
         // Create new previous matches for employees seated at the same table
-        List<PreviousMatch> newPreviousMatches = new ArrayList<>();
+        List<PreviousMatch.PreviousMatchId> newPreviousMatches = new ArrayList<>();
 
         // Create pairs for each table
         tableToEmployeesMap.values().forEach(employeesAtTable -> {
             for (int i = 0; i < employeesAtTable.size(); i++) {
                 for (int j = i + 1; j < employeesAtTable.size(); j++) {
                     UUID employeeId1 = employeesAtTable.get(i);
                     UUID employeeId2 = employeesAtTable.get(j);
-                    newPreviousMatches.add(new PreviousMatch(new PreviousMatch.PreviousMatchId(employeeId1, employeeId2, eventId)));
-                    newPreviousMatches.add(new PreviousMatch(new PreviousMatch.PreviousMatchId(employeeId2, employeeId1, eventId)));
+                    newPreviousMatches.add(new PreviousMatch.PreviousMatchId(employeeId1, employeeId2, eventId));
+                    newPreviousMatches.add(new PreviousMatch.PreviousMatchId(employeeId2, employeeId1, eventId));
                 }
             }
         });

backend/src/main/java/com/itestra/eep/sql/ddl.sql

@@ -152,6 +152,11 @@ CREATE INDEX idx_visitor_participation_event_profile ON organization.visitor_par
 CREATE INDEX idx_visitor_participation_invitor ON organization.visitor_participation (invitor_participation_id) WHERE invitor_participation_id IS NOT NULL;
 CREATE INDEX idx_visitor_participation_access_link ON organization.visitor_participation (access_link);
 --
+CREATE INDEX idx_previous_matches_first_employee ON organization.previous_matches (first_employee_id);
+CREATE INDEX idx_previous_matches_second_employee ON organization.previous_matches (second_employee_id);
+CREATE INDEX idx_previous_matches_event ON organization.previous_matches (event_id);
+CREATE INDEX idx_previous_matches_event_employees ON organization.previous_matches (first_employee_id, second_employee_id, event_id);
+--
 CREATE INDEX idx_files_event_id ON organization.files (event_id);
 CREATE INDEX idx_files_name ON organization.files (name);
 --