[0.8] Fix delete in-place multi swap (#539)

Fix delete in-place multi swap (#538)

fix bug in multi

(cherry picked from commit a4015a5)

Co-authored-by: alonre24 <alon.reshef@redis.com>

Author: github-actions[bot]

src/VecSim/algorithms/hnsw/hnsw_tiered.h

@@ -495,15 +495,17 @@ int TieredHNSWIndex<DataType, DistType>::deleteLabelFromHNSWInplace(labelType la
     auto *hnsw_index = this->getHNSWIndex();
 
     auto ids = hnsw_index->getElementIds(label);
-    hnsw_index->removeLabel(label);
-    // dispose pending repair and swap jobs for the removed ids.
+    // Dispose pending repair and swap jobs for the removed ids.
     vecsim_stl::vector<idType> idsToRemove(this->allocator);
     idsToRemove.reserve(ids.size());
     readySwapJobs += ids.size(); // account for the current ids that are going to be removed.
-    for (auto id : ids) {
+    for (size_t id_ind = 0; id_ind < ids.size(); id_ind++) {
+        // Get the id in every iteration, since the ids can be swapped in every iteration.
+        idType id = hnsw_index->getElementIds(label).at(id_ind);
         hnsw_index->removeVectorInPlace(id);
         this->executeSwapJob(id, idsToRemove);
     }
+    hnsw_index->removeLabel(label);
     for (idType id : idsToRemove) {
         idToSwapJob.erase(id);
     }

src/VecSim/algorithms/hnsw/hnsw_tiered_tests_friends.h

@@ -51,6 +51,7 @@ INDEX_TEST_FRIEND_CLASS(HNSWTieredIndexTestBasic_runGCAPI_Test)
 INDEX_TEST_FRIEND_CLASS(HNSWTieredIndexTestBasic_FitMemoryTest_Test)
 INDEX_TEST_FRIEND_CLASS(HNSWTieredIndexTestBasic_deleteBothAsyncAndInplace_Test)
 INDEX_TEST_FRIEND_CLASS(HNSWTieredIndexTestBasic_deleteBothAsyncAndInplaceMulti_Test)
+INDEX_TEST_FRIEND_CLASS(HNSWTieredIndexTestBasic_deleteInplaceMultiSwapId_Test)
 
 friend class BF16TieredTest;
 friend class FP16TieredTest;

tests/unit/test_hnsw_tiered.cpp

@@ -3655,3 +3655,26 @@ TYPED_TEST(HNSWTieredIndexTestBasic, deleteBothAsyncAndInplaceMulti) {
     // Id 1 is now ready due to the deletion of 0 and its associated jobs.
     ASSERT_EQ(tiered_index->readySwapJobs, 1);
 }
+
+TYPED_TEST(HNSWTieredIndexTestBasic, deleteInplaceMultiSwapId) {
+    // Create TieredHNSW index instance with a mock queue.
+    size_t dim = 4;
+    HNSWParams params = {
+        .type = TypeParam::get_index_type(), .dim = dim, .metric = VecSimMetric_L2, .multi = true};
+    VecSimParams hnsw_params = CreateParams(params);
+
+    auto mock_thread_pool = tieredIndexMock();
+
+    auto *tiered_index = this->CreateTieredHNSWIndex(hnsw_params, mock_thread_pool);
+    auto allocator = tiered_index->getAllocator();
+
+    // Insert three vector to HNSW - first and last under the same label.
+    GenerateAndAddVector<TEST_DATA_T>(tiered_index->backendIndex, dim, 0);
+    GenerateAndAddVector<TEST_DATA_T>(tiered_index->backendIndex, dim, 1);
+    GenerateAndAddVector<TEST_DATA_T>(tiered_index->backendIndex, dim, 0);
+    tiered_index->setWriteMode(VecSim_WriteInPlace);
+    // Delete in-place and validate that the second id of label 0 swapped properly with the last id
+    // before the deletion, and that eventually entry point was set correctly,
+    ASSERT_EQ(tiered_index->deleteVector(0), 2);
+    ASSERT_EQ(tiered_index->getHNSWIndex()->safeGetEntryPointState().first, 0);
+}