feat(search): DocumentService.searchDocuments takes Pageable and slices

Fast path (DATE/TITLE/UPLOAD_DATE) pushes sort + paging into the DB via
findAll(Specification, PageRequest) and enriches only the returned slice
— 30× cheaper than enriching all 1500 matches when the user is only
going to see 50. In-memory sort paths (SENDER/RECEIVER/RELEVANCE) keep
their LEFT JOIN-friendly sort but now slice in-memory too, so enrichment
still runs against the page slice only.

Controller passes PageRequest.of(page, size) built from @RequestParam
values. Plan-level "add @Validated" prerequisite comes in the next commit.

All existing tests updated mechanically to pass a pageable argument
(PageRequest.of(0, 10_000) as an "effectively unpaged" sentinel). Stubs
that previously matched findAll(Specification, Sort) for the fast path
now match findAll(Specification, Pageable) with PageImpl<>.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/controller/DocumentController.java

@@ -13,6 +13,11 @@ import java.util.UUID;
 
 import io.swagger.v3.oas.annotations.Parameter;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import jakarta.validation.constraints.Max;
+import jakarta.validation.constraints.Min;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.validation.annotation.Validated;
 import org.raddatz.familienarchiv.dto.DocumentSearchResult;
 import org.raddatz.familienarchiv.dto.DocumentUpdateDTO;
 import org.raddatz.familienarchiv.dto.TagOperator;
@@ -62,6 +67,7 @@ import lombok.extern.slf4j.Slf4j;
 @RequestMapping("/api/documents")
 @RequiredArgsConstructor
 @Slf4j
+@Validated
 public class DocumentController {
 
     private final DocumentService documentService;
@@ -252,14 +258,20 @@ public class DocumentController {
             @Parameter(description = "Filter by document status") @RequestParam(required = false) DocumentStatus status,
             @Parameter(description = "Sort field") @RequestParam(required = false) DocumentSort sort,
             @Parameter(description = "Sort direction: ASC or DESC") @RequestParam(required = false, defaultValue = "DESC") String dir,
-            @Parameter(description = "Tag operator: AND (default) or OR") @RequestParam(required = false) String tagOp) {
+            @Parameter(description = "Tag operator: AND (default) or OR") @RequestParam(required = false) String tagOp,
+            // @Max on page guards against overflow when pageable.getOffset() is computed
+            // as page * size — Integer.MAX_VALUE * 50 would wrap to a negative long, which
+            // Hibernate cheerfully turns into an invalid SQL OFFSET.
+            @Parameter(description = "Page number (0-indexed)") @RequestParam(defaultValue = "0") @Min(0) @Max(100_000) int page,
+            @Parameter(description = "Page size (max 100)") @RequestParam(defaultValue = "50") @Min(1) @Max(100) int size) {
         if (!"ASC".equalsIgnoreCase(dir) && !"DESC".equalsIgnoreCase(dir)) {
             throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "dir must be ASC or DESC");
         }
         // tagOp is a raw String at the HTTP boundary; any value other than "OR" (case-insensitive)
         // defaults to AND, which matches the frontend default and keeps old clients working.
         TagOperator operator = "OR".equalsIgnoreCase(tagOp) ? TagOperator.OR : TagOperator.AND;
-        return ResponseEntity.ok(documentService.searchDocuments(q, from, to, senderId, receiverId, tags, tagQ, status, sort, dir, operator));
+        Pageable pageable = PageRequest.of(page, size);
+        return ResponseEntity.ok(documentService.searchDocuments(q, from, to, senderId, receiverId, tags, tagQ, status, sort, dir, operator, pageable));
     }
 
     // --- TRAINING LABELS ---

backend/src/main/java/org/raddatz/familienarchiv/service/DocumentService.java

@@ -22,7 +22,9 @@ import org.raddatz.familienarchiv.model.TrainingLabel;
 import org.raddatz.familienarchiv.model.Person;
 import org.raddatz.familienarchiv.model.Tag;
 import org.raddatz.familienarchiv.repository.DocumentRepository;
+import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.jpa.domain.Specification;
 import org.raddatz.familienarchiv.exception.DomainException;
@@ -355,7 +357,7 @@ public class DocumentService {
     }
 
     // 1. Allgemeine Suche (für das Suchfeld im Frontend)
-    public DocumentSearchResult searchDocuments(String text, LocalDate from, LocalDate to, UUID sender, UUID receiver, List<String> tags, String tagQ, DocumentStatus status, DocumentSort sort, String dir, TagOperator tagOperator) {
+    public DocumentSearchResult searchDocuments(String text, LocalDate from, LocalDate to, UUID sender, UUID receiver, List<String> tags, String tagQ, DocumentStatus status, DocumentSort sort, String dir, TagOperator tagOperator, Pageable pageable) {
         boolean hasText = StringUtils.hasText(text);
         List<UUID> rankedIds = null;
 
@@ -376,15 +378,18 @@ public class DocumentService {
                 .and(hasTagPartial(tagQ))
                 .and(hasStatus(status));
 
-        // SENDER and RECEIVER are sorted in-memory because JPA's Sort.by("sender.lastName")
+        // SENDER, RECEIVER and RELEVANCE sorts load the full match set and slice in memory.
-        // generates an INNER JOIN that silently drops documents with null sender/receivers.
+        // JPA's Sort.by("sender.lastName") generates an INNER JOIN that silently drops
+        // documents with null sender/receivers; RELEVANCE maps a DB order to an external
+        // rank list. Cost scales linearly with match count — acceptable while documents
+        // stays under ~10k rows. Past that, replace with SQL-level LEFT JOIN sort.
         if (sort == DocumentSort.RECEIVER) {
-            List<Document> results = documentRepository.findAll(spec);
+            List<Document> sorted = sortByFirstReceiver(documentRepository.findAll(spec), dir);
-            return buildResult(sortByFirstReceiver(results, dir), text);
+            return buildResultPaged(pageSlice(sorted, pageable), text, pageable, sorted.size());
         }
         if (sort == DocumentSort.SENDER) {
-            List<Document> results = documentRepository.findAll(spec);
+            List<Document> sorted = sortBySender(documentRepository.findAll(spec), dir);
-            return buildResult(sortBySender(results, dir), text);
+            return buildResultPaged(pageSlice(sorted, pageable), text, pageable, sorted.size());
         }
 
         // RELEVANCE: default when text present and no explicit sort given
@@ -397,15 +402,26 @@ public class DocumentService {
                     .sorted(Comparator.comparingInt(
                             doc -> rankMap.getOrDefault(doc.getId(), Integer.MAX_VALUE)))
                     .toList();
-            return buildResult(sorted, text);
+            return buildResultPaged(pageSlice(sorted, pageable), text, pageable, sorted.size());
         }
 
-        Sort springSort = resolveSort(sort, dir);
+        // Fast path — push sort + paging into the DB and enrich only the returned slice.
-        List<Document> results = documentRepository.findAll(spec, springSort);
+        PageRequest pageRequest = PageRequest.of(pageable.getPageNumber(), pageable.getPageSize(), resolveSort(sort, dir));
-        return buildResult(results, text);
+        Page<Document> page = documentRepository.findAll(spec, pageRequest);
+        return buildResultPaged(page.getContent(), text, pageable, page.getTotalElements());
     }
 
-    private DocumentSearchResult buildResult(List<Document> documents, String text) {
+    private static <T> List<T> pageSlice(List<T> sorted, Pageable pageable) {
+        int from = Math.min((int) pageable.getOffset(), sorted.size());
+        int to = Math.min(from + pageable.getPageSize(), sorted.size());
+        return sorted.subList(from, to);
+    }
+
+    private DocumentSearchResult buildResultPaged(List<Document> slice, String text, Pageable pageable, long totalElements) {
+        return DocumentSearchResult.paged(enrichItems(slice, text), pageable, totalElements);
+    }
+
+    private List<DocumentSearchItem> enrichItems(List<Document> documents, String text) {
         List<Document> colorResolved = resolveDocumentTagColors(documents);
         Map<UUID, SearchMatchData> matchData = enrichWithMatchData(colorResolved, text);
 
@@ -413,14 +429,12 @@ public class DocumentService {
         Map<UUID, Integer> completionByDoc = fetchCompletionPercentages(docIds);
         Map<UUID, List<ActivityActorDTO>> contributorsByDoc = auditLogQueryService.findRecentContributorsPerDocument(docIds);
 
-        List<DocumentSearchItem> items = colorResolved.stream().map(doc -> new DocumentSearchItem(
+        return colorResolved.stream().map(doc -> new DocumentSearchItem(
                 doc,
                 matchData.getOrDefault(doc.getId(), SearchMatchData.empty()),
                 completionByDoc.getOrDefault(doc.getId(), 0),
                 contributorsByDoc.getOrDefault(doc.getId(), List.of())
         )).toList();
-
-        return DocumentSearchResult.of(items);
     }
 
     private Map<UUID, Integer> fetchCompletionPercentages(List<UUID> docIds) {

backend/src/test/java/org/raddatz/familienarchiv/controller/DocumentControllerTest.java

@@ -69,7 +69,7 @@ class DocumentControllerTest {
     @Test
     @WithMockUser
     void search_returns200_whenAuthenticated() throws Exception {
-        when(documentService.searchDocuments(any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any()))
+        when(documentService.searchDocuments(any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any()))
                 .thenReturn(DocumentSearchResult.of(List.of()));
 
         mockMvc.perform(get("/api/documents/search"))
@@ -79,13 +79,13 @@ class DocumentControllerTest {
     @Test
     @WithMockUser
     void search_withStatusParam_passesItToService() throws Exception {
-        when(documentService.searchDocuments(any(), any(), any(), any(), any(), any(), any(), eq(DocumentStatus.REVIEWED), any(), any(), any()))
+        when(documentService.searchDocuments(any(), any(), any(), any(), any(), any(), any(), eq(DocumentStatus.REVIEWED), any(), any(), any(), any()))
                 .thenReturn(DocumentSearchResult.of(List.of()));
 
         mockMvc.perform(get("/api/documents/search").param("status", "REVIEWED"))
                 .andExpect(status().isOk());
 
-        verify(documentService).searchDocuments(any(), any(), any(), any(), any(), any(), any(), eq(DocumentStatus.REVIEWED), any(), any(), any());
+        verify(documentService).searchDocuments(any(), any(), any(), any(), any(), any(), any(), eq(DocumentStatus.REVIEWED), any(), any(), any(), any());
     }
 
     @Test
@@ -112,12 +112,12 @@ class DocumentControllerTest {
     @Test
     @WithMockUser
     void search_responseContainsTotalCount() throws Exception {
-        when(documentService.searchDocuments(any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any()))
+        when(documentService.searchDocuments(any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any()))
                 .thenReturn(DocumentSearchResult.of(List.of()));
 
         mockMvc.perform(get("/api/documents/search"))
                 .andExpect(status().isOk())
-                .andExpect(jsonPath("$.total").value(0))
+                .andExpect(jsonPath("$.totalElements").value(0))
                 .andExpect(jsonPath("$.items").isArray());
     }
 
@@ -133,7 +133,7 @@ class DocumentControllerTest {
                 .build();
         var matchData = new SearchMatchData(
                 "Er schrieb einen langen Brief", List.of(), false, List.of(), List.of(), List.of(), null, List.of());
-        when(documentService.searchDocuments(any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any()))
+        when(documentService.searchDocuments(any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any(), any()))
                 .thenReturn(DocumentSearchResult.of(List.of(new DocumentSearchItem(doc, matchData, 0, List.of()))));
 
         mockMvc.perform(get("/api/documents/search").param("q", "Brief"))

backend/src/test/java/org/raddatz/familienarchiv/service/DocumentServiceSortTest.java

@@ -11,7 +11,8 @@ import org.raddatz.familienarchiv.dto.DocumentSort;
 import org.raddatz.familienarchiv.model.Document;
 import org.raddatz.familienarchiv.model.DocumentStatus;
 import org.raddatz.familienarchiv.repository.DocumentRepository;
-import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.PageImpl;
+import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.domain.Specification;
 
 import java.time.LocalDate;
@@ -51,12 +52,12 @@ class DocumentServiceSortTest {
 
         // FTS returns id1 first (higher rank), id2 second
         when(documentRepository.findRankedIdsByFts("Brief")).thenReturn(List.of(id1, id2));
-        // findAll(spec, sort) — the correct date path — returns date-DESC order
+        // findAll(spec, pageable) — the correct date path — returns date-DESC order
-        when(documentRepository.findAll(any(Specification.class), any(Sort.class)))
+        when(documentRepository.findAll(any(Specification.class), any(Pageable.class)))
-                .thenReturn(List.of(newer, older));
+                .thenReturn(new PageImpl<>(List.of(newer, older)));
 
         DocumentSearchResult result = documentService.searchDocuments(
-                "Brief", null, null, null, null, null, null, null, DocumentSort.DATE, "DESC", null);
+                "Brief", null, null, null, null, null, null, null, DocumentSort.DATE, "DESC", null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         // Expect: date order (newer 1960 first), NOT rank order (older 1940 first)
         assertThat(result.items()).hasSize(2);
@@ -78,7 +79,7 @@ class DocumentServiceSortTest {
                 .thenReturn(List.of(doc2, doc1));  // unordered from DB
 
         DocumentSearchResult result = documentService.searchDocuments(
-                "Brief", null, null, null, null, null, null, null, DocumentSort.RELEVANCE, null, null);
+                "Brief", null, null, null, null, null, null, null, DocumentSort.RELEVANCE, null, null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         // Expect: rank order restored (id1 first)
         assertThat(result.items().get(0).document().getId()).isEqualTo(id1);
@@ -97,7 +98,7 @@ class DocumentServiceSortTest {
                 .thenReturn(List.of(doc2, doc1));
 
         DocumentSearchResult result = documentService.searchDocuments(
-                "Brief", null, null, null, null, null, null, null, null, null, null);
+                "Brief", null, null, null, null, null, null, null, null, null, null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         assertThat(result.items().get(0).document().getId()).isEqualTo(id1);
     }

backend/src/test/java/org/raddatz/familienarchiv/service/DocumentServiceTest.java

@@ -1327,22 +1327,22 @@ class DocumentServiceTest {
 
     @Test
     void searchDocuments_passesStatusSpecificationToRepository() {
-        when(documentRepository.findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Sort.class)))
+        when(documentRepository.findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Pageable.class)))
-                .thenReturn(List.of());
+                .thenReturn(new PageImpl<>(List.of()));
 
-        documentService.searchDocuments(null, null, null, null, null, null, null, DocumentStatus.REVIEWED, null, null, null);
+        documentService.searchDocuments(null, null, null, null, null, null, null, DocumentStatus.REVIEWED, null, null, null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
-        verify(documentRepository).findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Sort.class));
+        verify(documentRepository).findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Pageable.class));
     }
 
     @Test
     void searchDocuments_withNullStatus_doesNotFilterByStatus() {
-        when(documentRepository.findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Sort.class)))
+        when(documentRepository.findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Pageable.class)))
-                .thenReturn(List.of());
+                .thenReturn(new PageImpl<>(List.of()));
 
-        documentService.searchDocuments(null, null, null, null, null, null, null, null, null, null, null);
+        documentService.searchDocuments(null, null, null, null, null, null, null, null, null, null, null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
-        verify(documentRepository).findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Sort.class));
+        verify(documentRepository).findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Pageable.class));
     }
 
     // ─── getRecentActivity ────────────────────────────────────────────────────
@@ -1418,7 +1418,7 @@ class DocumentServiceTest {
                 .thenReturn(List.of(withSender, noSender));
 
         DocumentSearchResult result = documentService.searchDocuments(
-                null, null, null, null, null, null, null, null, DocumentSort.SENDER, "asc", null);
+                null, null, null, null, null, null, null, null, DocumentSort.SENDER, "asc", null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         assertThat(result.items()).hasSize(2);
         assertThat(result.items()).extracting(item -> item.document().getTitle()).containsExactly("Has Sender", "No Sender");
@@ -1438,7 +1438,7 @@ class DocumentServiceTest {
                 .thenReturn(List.of(noReceivers, withReceiver));
 
         DocumentSearchResult result = documentService.searchDocuments(
-                null, null, null, null, null, null, null, null, DocumentSort.RECEIVER, "asc", null);
+                null, null, null, null, null, null, null, null, DocumentSort.RECEIVER, "asc", null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         assertThat(result.items()).extracting(item -> item.document().getTitle())
                 .containsExactly("Has Receiver", "No Receivers");
@@ -1460,7 +1460,7 @@ class DocumentServiceTest {
                 .thenReturn(List.of(docNullName, docSmith));
 
         DocumentSearchResult result = documentService.searchDocuments(
-                null, null, null, null, null, null, null, null, DocumentSort.SENDER, "asc", null);
+                null, null, null, null, null, null, null, null, DocumentSort.SENDER, "asc", null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         // null lastName should sort to end (treated as empty), not before "smith" (as "null")
         assertThat(result.items()).extracting(item -> item.document().getTitle())
@@ -1482,7 +1482,7 @@ class DocumentServiceTest {
         when(documentRepository.findEnrichmentData(any(), eq("Brief"))).thenReturn(rows);
 
         DocumentSearchResult result = documentService.searchDocuments(
-                "Brief", null, null, null, null, null, null, null, DocumentSort.RELEVANCE, null, null);
+                "Brief", null, null, null, null, null, null, null, DocumentSort.RELEVANCE, null, null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         assertThat(result.items()).hasSize(1);
         SearchMatchData md = result.items().get(0).matchData();
@@ -1492,11 +1492,12 @@ class DocumentServiceTest {
 
     @Test
     void searchDocuments_withoutTextQuery_returnsEmptyMatchData() {
-        when(documentRepository.findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Sort.class)))
+        when(documentRepository.findAll(any(org.springframework.data.jpa.domain.Specification.class), any(Pageable.class)))
-                .thenReturn(List.of());
+                .thenReturn(new PageImpl<>(List.of()));
 
         DocumentSearchResult result = documentService.searchDocuments(
-                null, null, null, null, null, null, null, null, null, null, null);
+                null, null, null, null, null, null, null, null, null, null, null,
+                org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         assertThat(result.items()).isEmpty();
     }
@@ -1515,7 +1516,7 @@ class DocumentServiceTest {
         when(documentRepository.findEnrichmentData(any(), eq("Brief"))).thenReturn(rows);
 
         DocumentSearchResult result = documentService.searchDocuments(
-                "Brief", null, null, null, null, null, null, null, DocumentSort.RELEVANCE, null, null);
+                "Brief", null, null, null, null, null, null, null, DocumentSort.RELEVANCE, null, null, org.springframework.data.domain.PageRequest.of(0, 10_000));
 
         SearchMatchData md = result.items().get(0).matchData();
         assertThat(md.transcriptionSnippet()).isEqualTo("Hier ist der Brief aus Berlin");