let the capacity of idToLabel in flat index be tight to the size. This requires changing a bit the logic of updating jobs id after removing a vector from flat buffer and swap ids. (#367)

Author: alonre24

src/VecSim/algorithms/brute_force/brute_force.h

@@ -57,13 +57,14 @@ class BruteForceIndex : public VecSimIndexAbstract<DistType> {
 
     inline vecsim_stl::vector<VectorBlock *> getVectorBlocks() const { return vectorBlocks; }
     inline const labelType getLabelByInternalId(idType internal_id) const {
-        return idToLabelMapping[internal_id];
+        return idToLabelMapping.at(internal_id);
     }
     // Remove a specific vector that is stored under a label from the index by its internal id.
     virtual int deleteVectorById(labelType label, idType id) = 0;
-    // Remove a vector and return a map between internal ids and the original internal ids that they
-    // hold AFTER the removals and swaps.
-    virtual std::unordered_map<idType, idType> deleteVectorAndGetUpdatedIds(labelType label) = 0;
+    // Remove a vector and return a map between internal ids and the original internal ids of the
+    // vector that they hold as a result of the overall removals and swaps, along with its label.
+    virtual std::unordered_map<idType, std::pair<idType, labelType>>
+    deleteVectorAndGetUpdatedIds(labelType label) = 0;
     // Check if a certain label exists in the index.
     virtual inline bool isLabelExists(labelType label) = 0;
     // Return a set of all labels that are stored in the index (helper for computing label count
@@ -160,6 +161,7 @@ void BruteForceIndex<DataType, DistType>::appendVector(const void *vector_data,
         size_t last_block_vectors_count = id % this->blockSize;
         this->idToLabelMapping.resize(
             idToLabelMapping_size + this->blockSize - last_block_vectors_count, 0);
+        this->idToLabelMapping.shrink_to_fit();
     }
 
     // add label to idToLabelMapping
@@ -210,10 +212,11 @@ void BruteForceIndex<DataType, DistType>::removeVector(idType id_to_delete) {
         // Resize and align the idToLabelMapping.
         size_t idToLabel_size = idToLabelMapping.size();
         // If the new size is smaller by at least one block comparing to the idToLabelMapping
-        // align to be a multiplication of blocksize  and resize by one block.
+        // align to be a multiplication of block size and resize by one block.
         if (this->count + this->blockSize <= idToLabel_size) {
             size_t vector_to_align_count = idToLabel_size % this->blockSize;
             this->idToLabelMapping.resize(idToLabel_size - this->blockSize - vector_to_align_count);
+            this->idToLabelMapping.shrink_to_fit();
         }
     }
 }

src/VecSim/algorithms/brute_force/brute_force_multi.h

@@ -34,7 +34,8 @@ class BruteForceIndex_Multi : public BruteForceIndex<DataType, DistType> {
         return std::unique_ptr<vecsim_stl::abstract_results_container>(
             new (this->allocator) vecsim_stl::unique_results_container(cap, this->allocator));
     }
-    std::unordered_map<idType, idType> deleteVectorAndGetUpdatedIds(labelType label) override;
+    std::unordered_map<idType, std::pair<idType, labelType>>
+    deleteVectorAndGetUpdatedIds(labelType label) override;
 #ifdef BUILD_TESTS
     void getDataByLabel(labelType label,
                         std::vector<std::vector<DataType>> &vectors_output) const override {
@@ -117,15 +118,15 @@ int BruteForceIndex_Multi<DataType, DistType>::deleteVector(labelType label) {
 }
 
 template <typename DataType, typename DistType>
-std::unordered_map<idType, idType>
+std::unordered_map<idType, std::pair<idType, labelType>>
 BruteForceIndex_Multi<DataType, DistType>::deleteVectorAndGetUpdatedIds(labelType label) {
     // Hold a mapping from ids that are removed and changed to the original ids that were swapped
     // into it. For example, if we have ids 0, 1, 2, 3, 4 and are about to remove ids 1, 3, 4, we
     // should get the following scenario: {1->4} => {1->4} => {1->2}.
     // Explanation: first we delete 1 and swap it with 4. Then, we remove 3 and have no swap since 3
     // is the last id. Lastly, we delete the original 4 which is now in id 1, and swap it with 2.
     // Eventually, in id 1 we should have the original vector whose id was 2.
-    std::unordered_map<idType, idType> updated_ids;
+    std::unordered_map<idType, std::pair<idType, labelType>> updated_ids;
 
     // Find the id to delete.
     auto deleted_label_ids_pair = this->labelToIdsLookup.find(label);
@@ -140,6 +141,7 @@ BruteForceIndex_Multi<DataType, DistType>::deleteVectorAndGetUpdatedIds(labelTyp
         // The removal take into consideration the current internal id to remove, even if it is not
         // the original id, and it has swapped into this id after previous swap of another id that
         // belongs to this label.
+        labelType last_id_label = this->idToLabelMapping[this->count - 1];
         this->removeVector(cur_id_to_delete);
         // If cur_id_to_delete exists in the map, remove it as it is no longer valid, whether it
         // will get a new value due to a swap, or it is the last element in the index.
@@ -151,7 +153,7 @@ BruteForceIndex_Multi<DataType, DistType>::deleteVectorAndGetUpdatedIds(labelTyp
                 updated_ids.erase(this->count);
             } else {
                 // Otherwise, the last id now resides where the deleted id was.
-                updated_ids[cur_id_to_delete] = this->count;
+                updated_ids[cur_id_to_delete] = {this->count, last_id_label};
             }
         }
     }

src/VecSim/algorithms/brute_force/brute_force_single.h

@@ -33,7 +33,8 @@ class BruteForceIndex_Single : public BruteForceIndex<DataType, DistType> {
     }
 
     inline size_t indexLabelCount() const override { return this->count; }
-    std::unordered_map<idType, idType> deleteVectorAndGetUpdatedIds(labelType label) override;
+    std::unordered_map<idType, std::pair<idType, labelType>>
+    deleteVectorAndGetUpdatedIds(labelType label) override;
 
     // We call this when we KNOW that the label exists in the index.
     idType getIdOfLabel(labelType label) const { return labelToIdLookup.find(label)->second; }
@@ -149,10 +150,10 @@ int BruteForceIndex_Single<DataType, DistType>::deleteVector(labelType label) {
 }
 
 template <typename DataType, typename DistType>
-std::unordered_map<idType, idType>
+std::unordered_map<idType, std::pair<idType, labelType>>
 BruteForceIndex_Single<DataType, DistType>::deleteVectorAndGetUpdatedIds(labelType label) {
 
-    std::unordered_map<idType, idType> updated_ids;
+    std::unordered_map<idType, std::pair<idType, labelType>> updated_ids;
     // Find the id to delete.
     auto deleted_label_id_pair = this->labelToIdLookup.find(label);
     if (deleted_label_id_pair == this->labelToIdLookup.end()) {
@@ -165,10 +166,10 @@ BruteForceIndex_Single<DataType, DistType>::deleteVectorAndGetUpdatedIds(labelTy
 
     // Remove the pair of the deleted vector.
     labelToIdLookup.erase(label);
-
-    this->removeVector(id_to_delete);
+    labelType last_id_label = this->idToLabelMapping[this->count - 1];
+    this->removeVector(id_to_delete); // this will decrease this->count and make the swap
     if (id_to_delete != this->count) {
-        updated_ids[id_to_delete] = this->count;
+        updated_ids[id_to_delete] = {this->count, last_id_label};
     }
     return updated_ids;
 }

src/VecSim/algorithms/hnsw/hnsw_tiered.h

@@ -100,7 +100,7 @@ class TieredHNSWIndex : public VecSimTieredIndex<DataType, DistType> {
     // label-to-insert-jobs lookup. Also, since deletion a vector triggers swapping of the
     // internal last id with the deleted vector id, here we update the pending insert job(s) for the
     // last id (if needed). This should be called while *flat lock is held* (exclusive lock).
-    void updateInsertJobInternalId(idType prev_id, idType new_id);
+    void updateInsertJobInternalId(idType prev_id, idType new_id, labelType label);
 
     // Helper function for performing in place mark delete of vector(s) associated with a label
     // and creating the appropriate repair jobs for the effected connections. This should be called
@@ -356,11 +356,11 @@ int TieredHNSWIndex<DataType, DistType>::deleteLabelFromHNSW(labelType label) {
 }
 
 template <typename DataType, typename DistType>
-void TieredHNSWIndex<DataType, DistType>::updateInsertJobInternalId(idType prev_id, idType new_id) {
+void TieredHNSWIndex<DataType, DistType>::updateInsertJobInternalId(idType prev_id, idType new_id,
+                                                                    labelType label) {
     // Update the pending job id, due to a swap that was caused after the removal of new_id.
     assert(new_id != INVALID_ID && prev_id != INVALID_ID);
-    labelType last_idx_label = this->frontendIndex->getLabelByInternalId(prev_id);
-    auto it = this->labelToInsertJobs.find(last_idx_label);
+    auto it = this->labelToInsertJobs.find(label);
     if (it != this->labelToInsertJobs.end()) {
         // There is a pending job for the label of the swapped last id - update its id.
         for (HNSWInsertJob *job_it : it->second) {
@@ -471,11 +471,17 @@ void TieredHNSWIndex<DataType, DistType>::executeInsertJob(HNSWInsertJob *job) {
         if (labelToInsertJobs.at(job->label).empty()) {
             labelToInsertJobs.erase(job->label);
         }
-        // Remove the vector from the flat buffer.
+        // Remove the vector from the flat buffer. This may cause the last vector id to swap with
+        // the deleted id. Hold the label for the last id, so we can later on update its
+        // corresponding job id. Note that after calling deleteVectorById, the last id's label
+        // shouldn't be available, since it is removed from the lookup.
+        labelType last_vec_label =
+            this->frontendIndex->getLabelByInternalId(this->frontendIndex->indexSize() - 1);
         int deleted = this->frontendIndex->deleteVectorById(job->label, job->id);
         if (deleted && job->id != this->frontendIndex->indexSize()) {
             // If the vector removal caused a swap with the last id, update the relevant insert job.
-            this->updateInsertJobInternalId(this->frontendIndex->indexSize(), job->id);
+            this->updateInsertJobInternalId(this->frontendIndex->indexSize(), job->id,
+                                            last_vec_label);
         }
     }
     this->flatIndexGuard.unlock();
@@ -700,7 +706,9 @@ int TieredHNSWIndex<DataType, DistType>::deleteVector(labelType label) {
             // an example in this function implementation in MULTI index).
             auto updated_ids = this->frontendIndex->deleteVectorAndGetUpdatedIds(label);
             for (auto &it : updated_ids) {
-                this->updateInsertJobInternalId(it.second, it.first);
+                idType prev_id = it.second.first;
+                labelType updated_vec_label = it.second.second;
+                this->updateInsertJobInternalId(prev_id, it.first, updated_vec_label);
             }
         }
         this->flatIndexGuard.unlock();

tests/unit/test_allocator.cpp

@@ -164,8 +164,8 @@ TYPED_TEST(IndexAllocatorTest, test_bf_index_block_size_1) {
     // collection allocate additional structures for their internal implementation.
     ASSERT_EQ(allocator->getAllocationSize(),
               expectedAllocationSize + deleteCommandAllocationDelta);
-    ASSERT_LE(expectedAllocationSize + expectedAllocationDelta, allocator->getAllocationSize());
-    ASSERT_LE(expectedAllocationDelta, deleteCommandAllocationDelta);
+    ASSERT_GE(expectedAllocationSize + expectedAllocationDelta, allocator->getAllocationSize());
+    ASSERT_GE(expectedAllocationDelta, deleteCommandAllocationDelta);
 
     info = bfIndex->info();
     ASSERT_EQ(allocator->getAllocationSize(), info.bfInfo.memory);

tests/unit/test_bruteforce.cpp

@@ -108,7 +108,7 @@ TYPED_TEST(BruteForceTest, brute_force_vector_update_test) {
 
 TYPED_TEST(BruteForceTest, resize_and_align_index) {
     size_t dim = 4;
-    size_t n = 15;
+    size_t n = 14;
     size_t blockSize = 10;
 
     BFParams params = {
@@ -134,24 +134,26 @@ TYPED_TEST(BruteForceTest, resize_and_align_index) {
 
     // Add another vector, since index size equals to the capacity, this should cause resizing
     // (to fit a multiplication of block_size).
-    GenerateAndAddVector<TEST_DATA_T>(index, dim, n + 1);
+    GenerateAndAddVector<TEST_DATA_T>(index, dim, n);
     ASSERT_EQ(VecSimIndex_IndexSize(index), n + 1);
     // Check new capacity size, should be blockSize * 2.
     ASSERT_EQ(bf_index->idToLabelMapping.size(), 2 * blockSize);
+    ASSERT_EQ(bf_index->idToLabelMapping.capacity(), 2 * blockSize);
 
-    // Now size = n + 1 = 16, capacity = 2* bs = 20. Test capacity overflow again
-    // to check that it stays aligned with blocksize.
+    // Now size = n + 1 (= 15), capacity = 2 * bs (= 20). Test capacity overflow again
+    // to check that it stays aligned with block size.
 
     size_t add_vectors_count = 8;
     for (size_t i = 0; i < add_vectors_count; i++) {
         GenerateAndAddVector<TEST_DATA_T>(index, dim, n + 2 + i, i);
     }
 
-    // Size should be n + 1 + 8 = 24.
+    // Size should be n + 1 + 8 (= 25).
     ASSERT_EQ(VecSimIndex_IndexSize(index), n + 1 + add_vectors_count);
 
     // Check new capacity size, should be blockSize * 3.
     ASSERT_EQ(bf_index->idToLabelMapping.size(), 3 * blockSize);
+    ASSERT_EQ(bf_index->idToLabelMapping.capacity(), 3 * blockSize);
 
     VecSimIndex_Free(index);
 }
@@ -170,7 +172,7 @@ TYPED_TEST(BruteForceTest, resize_and_align_index_largeInitialCapacity) {
     BruteForceIndex<TEST_DATA_T, TEST_DIST_T> *bf_index = this->CastToBF(index);
     ASSERT_EQ(VecSimIndex_IndexSize(index), 0);
 
-    // add up to blocksize + 1 = 3 + 1 = 4
+    // Add up to block size + 1 = 3 + 1 = 4
     for (size_t i = 0; i < bs + 1; i++) {
         GenerateAndAddVector<TEST_DATA_T>(index, dim, i, i);
     }
@@ -190,6 +192,7 @@ TYPED_TEST(BruteForceTest, resize_and_align_index_largeInitialCapacity) {
     // 10  - 3 - 10 % 3 (1) = 6
     idToLabelMapping_size = bf_index->idToLabelMapping.size();
     ASSERT_EQ(idToLabelMapping_size, n - bs - n % bs);
+    ASSERT_EQ(idToLabelMapping_size, bf_index->idToLabelMapping.capacity());
 
     // Delete all the vectors to decrease idToLabelMapping size by another bs.
     size_t i = 0;
@@ -198,19 +201,24 @@ TYPED_TEST(BruteForceTest, resize_and_align_index_largeInitialCapacity) {
         ++i;
     }
     ASSERT_EQ(bf_index->idToLabelMapping.size(), bs);
+    ASSERT_EQ(bf_index->idToLabelMapping.capacity(), bs);
+
     // Add and delete a vector to achieve:
     // size % block_size == 0 && size + bs <= idToLabelMapping_size(3).
     // idToLabelMapping_size should be resized to zero.
     GenerateAndAddVector<TEST_DATA_T>(index, dim, 0);
     VecSimIndex_DeleteVector(index, 0);
     ASSERT_EQ(bf_index->idToLabelMapping.size(), 0);
+    ASSERT_EQ(bf_index->idToLabelMapping.capacity(), 0);
 
     // Do it again. This time after adding a vector idToLabelMapping_size is increased by bs.
     // Upon deletion it will be resized to zero again.
     GenerateAndAddVector<TEST_DATA_T>(index, dim, 0);
     ASSERT_EQ(bf_index->idToLabelMapping.size(), bs);
+    ASSERT_EQ(bf_index->idToLabelMapping.capacity(), bs);
     VecSimIndex_DeleteVector(index, 0);
     ASSERT_EQ(bf_index->idToLabelMapping.size(), 0);
+    ASSERT_EQ(bf_index->idToLabelMapping.capacity(), 0);
 
     VecSimIndex_Free(index);
 }

tests/unit/test_hnsw_tiered.cpp

@@ -1601,9 +1601,9 @@ TYPED_TEST(HNSWTieredIndexTestBasic, deleteVectorMultiFromFlatAdvanced) {
     ASSERT_EQ(tiered_index->labelToInsertJobs.erase(vec_label_second), 1);
     auto updated_ids = tiered_index->frontendIndex->deleteVectorAndGetUpdatedIds(vec_label_second);
     ASSERT_EQ(updated_ids.size(), 1);
-    ASSERT_EQ(updated_ids.at(1), 2);
+    ASSERT_EQ(updated_ids.at(1).first, 2);
     for (auto &it : updated_ids) {
-        tiered_index->updateInsertJobInternalId(it.second, it.first);
+        tiered_index->updateInsertJobInternalId(it.second.first, it.first, it.second.second);
     }
     ASSERT_EQ(tiered_index->labelToInsertJobs.size(), 1);
     ASSERT_EQ(tiered_index->labelToInsertJobs.at(vec_label_first).size(), 2);
@@ -1633,9 +1633,9 @@ TYPED_TEST(HNSWTieredIndexTestBasic, deleteVectorMultiFromFlatAdvanced) {
     ASSERT_EQ(tiered_index->labelToInsertJobs.erase(vec_label_second), 1);
     updated_ids = tiered_index->frontendIndex->deleteVectorAndGetUpdatedIds(vec_label_second);
     ASSERT_EQ(updated_ids.size(), 1);
-    ASSERT_EQ(updated_ids.at(1), 3);
+    ASSERT_EQ(updated_ids.at(1).first, 3);
     for (auto &it : updated_ids) {
-        tiered_index->updateInsertJobInternalId(it.second, it.first);
+        tiered_index->updateInsertJobInternalId(it.second.first, it.first, it.second.second);
     }
     ASSERT_EQ(tiered_index->labelToInsertJobs.size(), 1);
     ASSERT_EQ(tiered_index->labelToInsertJobs.at(vec_label_first).size(), 2);