[MOD-12346] Remove main-thread graph repair from SVS delete operations (#831)

* remove consolidate from delete

* indexSize -> includes marked deleted
indexLabelCount -> only valid vectors

* fix flow tests

* Revert "fix flow tests"

This reverts commit 831c08c.

* Revert "indexSize -> includes marked deleted"

This reverts commit 82758c2.

* TO REVERT: bump to main SVS

* BUMP TO ib/buffer

* SVS v0.0.11: take updated bunaries and SVS public

* Reapply "indexSize -> includes marked deleted"

This reverts commit 3ae28cd.

* Reapply "fix flow tests"

This reverts commit 45462d4.

Author: meiravgri

src/VecSim/algorithms/svs/svs.h

@@ -240,7 +240,7 @@ class SVSIndex : public VecSimIndexAbstract<svs_details::vecsim_dt<DataType>, fl
     }
 
     int deleteVectorsImpl(const labelType *labels, size_t n) {
-        if (indexSize() == 0) {
+        if (indexLabelCount() == 0) {
             return 0;
         }
 
@@ -280,22 +280,13 @@ class SVSIndex : public VecSimIndexAbstract<svs_details::vecsim_dt<DataType>, fl
             return;
 
         // SVS index instance should not be empty
-        if (indexSize() == 0) {
+        if (indexLabelCount() == 0) {
             this->impl_.reset();
             num_marked_deleted = 0;
             return;
         }
 
         num_marked_deleted += n;
-        // consolidate index if number of changes bigger than 50% of index size
-        const float consolidation_threshold = .5f;
-        // indexSize() should not be 0 see above lines
-        assert(indexSize() > 0);
-        // Note: if this function is called after deleteVectorsImpl, indexSize is already updated
-        if (static_cast<float>(num_marked_deleted) / indexSize() > consolidation_threshold) {
-            impl_->consolidate();
-            num_marked_deleted = 0;
-        }
     }
 
     bool isTwoLevelLVQ(const VecSimSvsQuantBits &qbits) {
@@ -330,7 +321,7 @@ class SVSIndex : public VecSimIndexAbstract<svs_details::vecsim_dt<DataType>, fl
 
     ~SVSIndex() = default;
 
-    size_t indexSize() const override { return impl_ ? impl_->size() : 0; }
+    size_t indexSize() const override { return indexStorageSize(); }
 
     size_t indexStorageSize() const override { return impl_ ? impl_->view_data().size() : 0; }
 
@@ -342,7 +333,7 @@ class SVSIndex : public VecSimIndexAbstract<svs_details::vecsim_dt<DataType>, fl
         if constexpr (isMulti) {
             return impl_ ? impl_->labelcount() : 0;
         } else {
-            return indexSize();
+            return impl_ ? impl_->size() : 0;
         }
     }
 
@@ -524,7 +515,7 @@ class SVSIndex : public VecSimIndexAbstract<svs_details::vecsim_dt<DataType>, fl
                                 VecSimQueryParams *queryParams) const override {
         auto rep = new VecSimQueryReply(this->allocator);
         this->lastMode = STANDARD_KNN;
-        if (k == 0 || this->indexSize() == 0) {
+        if (k == 0 || this->indexLabelCount() == 0) {
             return rep;
         }
 
@@ -569,7 +560,7 @@ class SVSIndex : public VecSimIndexAbstract<svs_details::vecsim_dt<DataType>, fl
                                  VecSimQueryParams *queryParams) const override {
         auto rep = new VecSimQueryReply(this->allocator);
         this->lastMode = RANGE_QUERY;
-        if (radius == 0 || this->indexSize() == 0) {
+        if (radius == 0 || this->indexLabelCount() == 0) {
             return rep;
         }
 
@@ -642,7 +633,7 @@ class SVSIndex : public VecSimIndexAbstract<svs_details::vecsim_dt<DataType>, fl
         // take ownership of the blob copy and pass it to the batch iterator.
         auto *queryBlobCopyPtr = queryBlobCopy.release();
         // Ownership of queryBlobCopy moves to VecSimBatchIterator that will free it at the end.
-        if (indexSize() == 0) {
+        if (indexLabelCount() == 0) {
             return new (this->getAllocator())
                 NullSVS_BatchIterator(queryBlobCopyPtr, queryParams, this->getAllocator());
         } else {
@@ -652,7 +643,7 @@ class SVSIndex : public VecSimIndexAbstract<svs_details::vecsim_dt<DataType>, fl
     }
 
     bool preferAdHocSearch(size_t subsetSize, size_t k, bool initial_check) const override {
-        size_t index_size = this->indexSize();
+        size_t index_size = this->indexLabelCount();
 
         // Calculate the ratio of the subset size to the total index size.
         double subsetRatio = (index_size == 0) ? 0.f : static_cast<double>(subsetSize) / index_size;

tests/flow/test_svs_tiered.py

@@ -404,7 +404,7 @@ def test_recall_after_deletion(test_logger):
     test_logger.info(f"Done deleting half of the index")
     assert index.svs_label_count() >= (num_elements // 2) - indices_ctx.tiered_svs_params.updateTriggerThreshold
     assert index.svs_label_count() <= (num_elements // 2) + indices_ctx.tiered_svs_params.updateTriggerThreshold
-    assert svs_index.index_size() == (num_elements // 2)
+    assert svs_index.index_size() == num_elements
 
     # Create a list of tuples of the vectors that left.
     vectors = [vectors[i] for i in range(1, num_elements, 2)]

tests/unit/test_svs.cpp

@@ -262,20 +262,18 @@ TYPED_TEST(SVSTest, svs_bulk_vectors_add_delete_test) {
     runTopKSearchTest(index, query, k, verify_res, nullptr, BY_ID);
 
     // Delete almost all vectors
-    // First delete small amount of vector to prevent consolidation.
-    const size_t first_batch_deletion = 10;
-    ASSERT_EQ(svs_index->deleteVectors(ids.data(), first_batch_deletion), first_batch_deletion);
-    ASSERT_EQ(VecSimIndex_IndexSize(index), n - first_batch_deletion);
-    ASSERT_EQ(svs_index->getNumMarkedDeleted(), first_batch_deletion);
-
-    // Now delete enough vectors to trigger consolidation.
     const size_t keep_num = 1;
-    ASSERT_EQ(svs_index->deleteVectors(ids.data() + first_batch_deletion,
-                                       n - keep_num - first_batch_deletion),
-              n - keep_num - first_batch_deletion);
-    ASSERT_EQ(VecSimIndex_IndexSize(index), keep_num);
-    ASSERT_EQ(svs_index->getNumMarkedDeleted(), 0);
+    ASSERT_EQ(svs_index->deleteVectors(ids.data(), n - keep_num), n - keep_num);
+    ASSERT_EQ(VecSimIndex_IndexSize(index), n);
+    ASSERT_EQ(index->indexLabelCount(), keep_num);
+    ASSERT_EQ(svs_index->getNumMarkedDeleted(), n - keep_num);
 
+    // Delete rest of the vectors
+    // num_marked_deleted should reset.
+    ASSERT_EQ(svs_index->deleteVectors(ids.data() + n - keep_num, keep_num), keep_num);
+    ASSERT_EQ(VecSimIndex_IndexSize(index), 0);
+    ASSERT_EQ(index->indexLabelCount(), 0);
+    ASSERT_EQ(svs_index->getNumMarkedDeleted(), 0);
     VecSimIndex_Free(index);
 }
 
@@ -453,14 +451,18 @@ TYPED_TEST(SVSTest, svs_reindexing_same_vector) {
     for (size_t i = 0; i < n - 1; i++) {
         VecSimIndex_DeleteVector(index, i);
     }
-    ASSERT_EQ(VecSimIndex_IndexSize(index), 1);
+    ASSERT_EQ(VecSimIndex_IndexSize(index), n);
+    ASSERT_EQ(index->indexLabelCount(), 1);
+    ASSERT_EQ(svs_index->getNumMarkedDeleted(), n - 1);
 
     // Reinsert the same vectors under the same ids.
     for (size_t i = 0; i < n; i++) {
         // i / 10 is in integer (take the "floor value).
         GenerateAndAddVector<TEST_DATA_T>(index, dim, i, i / 10);
     }
-    ASSERT_EQ(VecSimIndex_IndexSize(index), n);
+    ASSERT_EQ(VecSimIndex_IndexSize(index), 2 * n);
+    ASSERT_EQ(index->indexLabelCount(), n);
+    ASSERT_EQ(svs_index->getNumMarkedDeleted(), n);
 
     // Run the same query again.
     runTopKSearchTest(index, query, k, verify_res);
@@ -513,14 +515,18 @@ TYPED_TEST(SVSTest, svs_reindexing_same_vector_different_id) {
     for (size_t i = 0; i < n - 1; i++) {
         VecSimIndex_DeleteVector(index, i);
     }
-    ASSERT_EQ(VecSimIndex_IndexSize(index), 1);
+    ASSERT_EQ(VecSimIndex_IndexSize(index), n);
+    ASSERT_EQ(index->indexLabelCount(), 1);
+    ASSERT_EQ(svs_index->getNumMarkedDeleted(), n - 1);
 
     // Reinsert the same vectors under different ids than before.
     for (size_t i = 0; i < n; i++) {
         GenerateAndAddVector<TEST_DATA_T>(index, dim, i + 10,
                                           i / 10); // i / 10 is in integer (take the "floor" value).
     }
-    ASSERT_EQ(VecSimIndex_IndexSize(index), n);
+    ASSERT_EQ(VecSimIndex_IndexSize(index), 2 * n);
+    ASSERT_EQ(index->indexLabelCount(), n);
+    ASSERT_EQ(svs_index->getNumMarkedDeleted(), n);
 
     // Run the same query again.
     auto verify_res_different_id = [&](size_t id, double score, size_t index) {
@@ -922,7 +928,8 @@ TYPED_TEST(SVSTest, test_delete_vector) {
 
     // Here the shift should happen.
     VecSimIndex_DeleteVector(index, 1);
-    ASSERT_EQ(VecSimIndex_IndexSize(index), n - 1);
+    ASSERT_EQ(VecSimIndex_IndexSize(index), n);
+    ASSERT_EQ(index->indexLabelCount(), n - 1);
 
     TEST_DATA_T query[] = {0.0, 0.0};
     auto verify_res = [&](size_t id, double score, size_t index) {
@@ -3026,7 +3033,8 @@ TYPED_TEST(SVSTest, logging_runtime_params) {
         index->addVector(v[i].data(), ids[i]);
     }
     ASSERT_EQ(svs_index->getNumMarkedDeleted(), 10);
-    ASSERT_EQ(VecSimIndex_IndexSize(index), n);
+    ASSERT_EQ(VecSimIndex_IndexSize(index), n + 10);
+    ASSERT_EQ(index->indexLabelCount(), n);
 
     float query[] = {50, 50, 50, 50};
     auto verify_res = [&](size_t id, double score, size_t index) { EXPECT_EQ(id, (index + 45)); };

tests/unit/test_svs_multi.cpp

@@ -536,7 +536,7 @@ TYPED_TEST(SVSMultiTest, test_dynamic_svs_info_iterator) {
     VecSimIndex_DeleteVector(index, 0);
     info = VecSimIndex_DebugInfo(index);
     infoIter = VecSimIndex_DebugInfoIterator(index);
-    ASSERT_EQ(2, info.commonInfo.indexSize);
+    ASSERT_EQ(4, info.commonInfo.indexSize);
     ASSERT_EQ(1, info.commonInfo.indexLabelCount);
     compareSVSIndexInfoToIterator(info, infoIter);
     VecSimDebugInfoIterator_Free(infoIter);

tests/unit/test_svs_tiered.cpp

@@ -894,7 +894,7 @@ TYPED_TEST(SVSTieredIndexTestBasic, KNNSearch) {
         VecSimIndex_DeleteVector(svs_index, i);
     }
     ASSERT_EQ(flat_index->indexSize(), n * 2 / 3);
-    ASSERT_EQ(svs_index->indexSize(), n / 2);
+    ASSERT_EQ(svs_index->indexLabelCount(), n / 2);
     k = n * 2 / 3;
     cur_memory_usage = allocator->getAllocationSize();
     runTopKSearchTest(tiered_index, query_0, k, ver_res_0);
@@ -909,7 +909,7 @@ TYPED_TEST(SVSTieredIndexTestBasic, KNNSearch) {
         VecSimIndex_DeleteVector(flat_index, i);
     }
     ASSERT_EQ(flat_index->indexSize(), n / 6);
-    ASSERT_EQ(svs_index->indexSize(), n / 2);
+    ASSERT_EQ(svs_index->indexLabelCount(), n / 2);
     k = n / 4;
     cur_memory_usage = allocator->getAllocationSize();
     runTopKSearchTest(tiered_index, query_0, k, ver_res_0);
@@ -923,7 +923,7 @@ TYPED_TEST(SVSTieredIndexTestBasic, KNNSearch) {
         GenerateAndAddVector<TEST_DATA_T>(flat_index, dim, i, i);
     }
     ASSERT_EQ(flat_index->indexSize(), n * 2 / 3);
-    ASSERT_EQ(svs_index->indexSize(), 0);
+    ASSERT_EQ(svs_index->indexLabelCount(), 0);
     k = n / 3;
     cur_memory_usage = allocator->getAllocationSize();
     runTopKSearchTest(tiered_index, query_0, k, ver_res_0);
@@ -1133,27 +1133,33 @@ TYPED_TEST(SVSTieredIndexTestBasic, markedDeleted) {
 
     // Override a vector while in the backend
     GenerateAndAddVector<TEST_DATA_T>(tiered_index, dim, 1);
-    ASSERT_EQ(tiered_index->indexSize(), n);
+    ASSERT_EQ(tiered_index->indexSize(), n + 1);
+    ASSERT_EQ(tiered_index->indexLabelCount(), n);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexLabelCount(), n - 1);
     ASSERT_EQ(tiered_index->getNumMarkedDeleted(), 1);
     ASSERT_EQ(tiered_index->GetSVSIndex()->getNumMarkedDeleted(), 1);
 
-    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n - 1);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n);
     ASSERT_EQ(tiered_index->GetFlatIndex()->indexSize(), 1);
 
     // Delete the overriden vector
     VecSimIndex_DeleteVector(tiered_index, 1);
-    ASSERT_EQ(tiered_index->indexSize(), n - 1);
+    ASSERT_EQ(tiered_index->indexSize(), n);
     ASSERT_EQ(tiered_index->getNumMarkedDeleted(), 1);
     ASSERT_EQ(tiered_index->GetSVSIndex()->getNumMarkedDeleted(), 1);
-    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n - 1);
+    ASSERT_EQ(tiered_index->indexLabelCount(), n - 1);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexLabelCount(), n - 1);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n);
     ASSERT_EQ(tiered_index->GetFlatIndex()->indexSize(), 0);
 
-    // Delete another arbirtrary vector
+    // Delete another arbitrary vector
     VecSimIndex_DeleteVector(tiered_index, 0);
-    ASSERT_EQ(tiered_index->indexSize(), n - 2);
+    ASSERT_EQ(tiered_index->indexSize(), n);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexLabelCount(), n - 2);
+    ASSERT_EQ(tiered_index->indexLabelCount(), n - 2);
     ASSERT_EQ(tiered_index->getNumMarkedDeleted(), 2);
     ASSERT_EQ(tiered_index->GetSVSIndex()->getNumMarkedDeleted(), 2);
-    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n - 2);
     ASSERT_EQ(tiered_index->GetFlatIndex()->indexSize(), 0);
 
     // Empty Index
@@ -1167,6 +1173,8 @@ TYPED_TEST(SVSTieredIndexTestBasic, markedDeleted) {
     ASSERT_EQ(tiered_index->GetSVSIndex()->getNumMarkedDeleted(), 0);
     ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), 0);
     ASSERT_EQ(tiered_index->GetFlatIndex()->indexSize(), 0);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexLabelCount(), 0);
+    ASSERT_EQ(tiered_index->indexLabelCount(), 0);
 }
 
 TYPED_TEST(SVSTieredIndexTestBasic, deleteVectorMulti) {
@@ -2917,18 +2925,26 @@ TYPED_TEST(SVSTieredIndexTest, writeInPlaceMode) {
     ASSERT_EQ(tiered_index->GetFlatIndex()->indexSize(), 0);
 
     // Overwrite inplace - only in single-value mode
+    size_t expected_marked_deleted = 0;
     if (!TypeParam::isMulti()) {
         TEST_DATA_T overwritten_vec[] = {1, 1, 1, 1};
         tiered_index->addVector(overwritten_vec, vec_label);
-        ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), 2);
+        expected_marked_deleted++;
+        ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), 3);
+        ASSERT_EQ(tiered_index->indexSize(), 3);
+        ASSERT_EQ(tiered_index->indexLabelCount(), 2);
         ASSERT_EQ(tiered_index->GetFlatIndex()->indexSize(), 0);
         ASSERT_EQ(tiered_index->getDistanceFrom_Unsafe(vec_label, overwritten_vec), 0);
+        ASSERT_EQ(tiered_index->GetSVSIndex()->getNumMarkedDeleted(), expected_marked_deleted);
     }
-    // Validate that the vector is removed in place.
+    // Validate that the vector is marked as deleted.
     tiered_index->deleteVector(vec_label);
-    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), 1);
-    ASSERT_EQ(tiered_index->GetSVSIndex()->getNumMarkedDeleted(), 0);
-    EXPECT_EQ(tiered_index->statisticInfo().numberOfMarkedDeleted, 0);
+    expected_marked_deleted++;
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), TypeParam::isMulti() ? 2 : 3);
+    ASSERT_EQ(tiered_index->indexLabelCount(), 1);
+
+    ASSERT_EQ(tiered_index->GetSVSIndex()->getNumMarkedDeleted(), expected_marked_deleted);
+    EXPECT_EQ(tiered_index->statisticInfo().numberOfMarkedDeleted, expected_marked_deleted);
 }
 
 TYPED_TEST(SVSTieredIndexTest, switchWriteModes) {
@@ -3024,7 +3040,7 @@ TYPED_TEST(SVSTieredIndexTest, switchWriteModes) {
     mock_thread_pool.thread_pool_join();
     // Verify that vectors were moved to SVS as expected
     auto sz_f = tiered_index->GetFlatIndex()->indexSize();
-    auto sz_b = tiered_index->GetBackendIndex()->indexSize();
+    auto sz_b = tiered_index->GetBackendIndex()->indexLabelCount();
     EXPECT_LE(sz_f, this->getUpdateThreshold());
     if (TypeParam::isMulti()) {
         ASSERT_EQ(tiered_index->indexLabelCount(), 2 * n_labels);
@@ -3097,25 +3113,23 @@ TYPED_TEST(SVSTieredIndexTestBasic, runGCAPI) {
     ASSERT_EQ(tiered_index->indexSize(), n);
     ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n);
 
-    // Delete all the vectors and wait for the thread pool to finish running the update jobs.
     for (size_t i = 0; i < threshold; i++) {
         tiered_index->deleteVector(i);
     }
     ASSERT_EQ(tiered_index->GetSVSIndex()->getNumMarkedDeleted(), threshold);
     EXPECT_EQ(tiered_index->statisticInfo().numberOfMarkedDeleted, threshold);
 
-    // Launch the BG threads loop that takes jobs from the queue and executes them.
-    mock_thread_pool.init_threads();
-    mock_thread_pool.thread_pool_join();
-
-    ASSERT_EQ(tiered_index->indexSize(), n - threshold);
+    ASSERT_EQ(tiered_index->indexSize(), n);
+    ASSERT_EQ(tiered_index->indexLabelCount(), n - threshold);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexLabelCount(), n - threshold);
     ASSERT_EQ(tiered_index->GetSVSIndex()->indexStorageSize(), n);
-    ASSERT_EQ(mock_thread_pool.jobQ.size(), 0);
     auto size_before_gc = tiered_index->getAllocationSize();
 
     // Run the GC API call, expect that we will clean up the SVS index.
     VecSimTieredIndex_GC(tiered_index);
     ASSERT_EQ(tiered_index->indexSize(), n - threshold);
+    ASSERT_EQ(tiered_index->GetBackendIndex()->indexSize(), n - threshold);
     ASSERT_EQ(tiered_index->GetSVSIndex()->indexStorageSize(), n - threshold);
     auto size_after_gc = tiered_index->getAllocationSize();
     // Expect that the size of the index was reduced.
@@ -3177,7 +3191,7 @@ TYPED_TEST(SVSTieredIndexTestBasic, switchDeleteModes) {
     mock_thread_pool.thread_pool_join();
     // Verify that vectors were moved to SVS as expected
     auto sz_f = tiered_index->GetFlatIndex()->indexSize();
-    auto sz_b = tiered_index->GetBackendIndex()->indexSize();
+    auto sz_b = tiered_index->GetBackendIndex()->indexLabelCount();
     EXPECT_LE(sz_f, update_threshold);
     EXPECT_EQ(sz_f + sz_b, n);
 }
@@ -3270,14 +3284,17 @@ TYPED_TEST(SVSTieredIndexTestBasic, testSwapJournalSingle) {
     // For single-value index, following vectors should be in the index:
     // 0:deleted, 1: 10, 2: deleted, 3:3, ..., n-2:deleted n-1: 10(n-1), n+1: n+1;
     // total: n-2 vectors and labels
-    ASSERT_EQ(tiered_index->indexSize(), n - 2);
     ASSERT_EQ(tiered_index->indexLabelCount(), n - 2);
+    EXPECT_EQ(tiered_index->GetBackendIndex()->indexLabelCount(), n - 5);
 
+    // We added 3 vectors to the flat index and removed 5 vectors from the backend index.
     // Backend index: 0:deleted, 1:deleted, 2:deleted, 3:3, ..., n-2:deleted, n-1:deleted;
     // total: n-5
-    EXPECT_EQ(tiered_index->GetBackendIndex()->indexSize(), n - 5);
+    EXPECT_EQ(tiered_index->GetBackendIndex()->indexSize(), n);
+    ASSERT_EQ(tiered_index->getNumMarkedDeleted(), 5);
     // Frontend index: 1:10, n-1:10(n-1), n+1:n+1
     ASSERT_EQ(tiered_index->GetFlatIndex()->indexSize(), 3);
+    ASSERT_EQ(tiered_index->indexSize(), n + tiered_index->GetFlatIndex()->indexSize());
 
     double abs_err = 1e-2; // Allow a larger relative error for quantization.
     TEST_DATA_T expected_vector[dim];
@@ -3401,13 +3418,16 @@ TYPED_TEST(SVSTieredIndexTestBasic, testSwapJournalMulti) {
     // For multi-value index, following vectors should be in the index:
     // 0: deleted, 1: (1,10), 2: deleted, 3:3, ..., n-2: deleted n-1: 10(n-1), n+1: n+1;
     // total: n-2 labels, n-1 vectors
-    ASSERT_EQ(tiered_index->indexSize(), n - 1);
     ASSERT_EQ(tiered_index->indexLabelCount(), n - 2);
+    EXPECT_EQ(tiered_index->GetBackendIndex()->indexLabelCount(), n - 4);
 
+    // We added 3 vectors to the flat index and removed 4 vectors from the backend index.
     // Backend index: 0:deleted, 1:1, 2:deleted, 3:3, ..., n-2:deleted, n-1:deleted; total: n-4
-    EXPECT_EQ(tiered_index->GetBackendIndex()->indexSize(), n - 4);
+    EXPECT_EQ(tiered_index->GetBackendIndex()->indexSize(), n);
+    ASSERT_EQ(tiered_index->getNumMarkedDeleted(), 4);
     // Frontend index: 1:10, n-1:10(n-1), n+1:n+1
     ASSERT_EQ(tiered_index->GetFlatIndex()->indexSize(), 3);
+    ASSERT_EQ(tiered_index->indexSize(), n + tiered_index->GetFlatIndex()->indexSize());
 
     double abs_err = 1e-2; // Allow a larger relative error for quantization.
     TEST_DATA_T expected_vector[dim];