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feat: add high-performance HNSW RaBitQ index #1798

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1 change: 1 addition & 0 deletions include/knowhere/comp/index_param.h
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,7 @@ constexpr const char* INDEX_HNSW = "HNSW";
constexpr const char* INDEX_HNSW_SQ = "HNSW_SQ";
constexpr const char* INDEX_HNSW_PQ = "HNSW_PQ";
constexpr const char* INDEX_HNSW_PRQ = "HNSW_PRQ";
constexpr const char* INDEX_HNSW_RABITQ = "HNSW_RABITQ";

constexpr const char* INDEX_DISKANN = "DISKANN";
constexpr const char* INDEX_AISAQ = "AISAQ";
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5 changes: 5 additions & 0 deletions include/knowhere/index/index_node_data_mock_wrapper.h
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Expand Up @@ -76,6 +76,11 @@ class IndexNodeDataMockWrapper : public IndexNode {
return index_node_->HasRawData(metric_type);
}

bool
IsIndexRefineEnabled() const override {
return index_node_->IsIndexRefineEnabled();
}

expected<DataSetPtr>
GetIndexMeta(std::unique_ptr<Config> cfg) const override {
return index_node_->GetIndexMeta(std::move(cfg));
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5 changes: 5 additions & 0 deletions include/knowhere/index/index_node_thread_pool_wrapper.h
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Expand Up @@ -57,6 +57,11 @@ class IndexNodeThreadPoolWrapper : public IndexNode {
return index_node_->HasRawData(metric_type);
}

bool
IsIndexRefineEnabled() const override {
return index_node_->IsIndexRefineEnabled();
}

expected<DataSetPtr>
GetIndexMeta(std::unique_ptr<Config> cfg) const override {
return index_node_->GetIndexMeta(std::move(cfg));
Expand Down
4 changes: 4 additions & 0 deletions include/knowhere/index/index_table.h
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Expand Up @@ -105,6 +105,10 @@ static std::set<std::pair<std::string, VecType>> legal_knowhere_index = {
{IndexEnum::INDEX_HNSW_PRQ, VecType::VECTOR_BFLOAT16},
{IndexEnum::INDEX_HNSW_PRQ, VecType::VECTOR_INT8},

{IndexEnum::INDEX_HNSW_RABITQ, VecType::VECTOR_FLOAT},
{IndexEnum::INDEX_HNSW_RABITQ, VecType::VECTOR_FLOAT16},
{IndexEnum::INDEX_HNSW_RABITQ, VecType::VECTOR_BFLOAT16},

// diskann
{IndexEnum::INDEX_DISKANN, VecType::VECTOR_FLOAT},
{IndexEnum::INDEX_DISKANN, VecType::VECTOR_FLOAT16},
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1 change: 1 addition & 0 deletions src/common/prometheus_client.cc
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Expand Up @@ -57,6 +57,7 @@ KnownIndexTypes() {
IndexEnum::INDEX_HNSW_SQ,
IndexEnum::INDEX_HNSW_PQ,
IndexEnum::INDEX_HNSW_PRQ,
IndexEnum::INDEX_HNSW_RABITQ,
IndexEnum::INDEX_DISKANN,
IndexEnum::INDEX_AISAQ,
IndexEnum::INDEX_MINHASH_LSH,
Expand Down
258 changes: 251 additions & 7 deletions src/index/hnsw/faiss_hnsw.cc
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Expand Up @@ -9,10 +9,13 @@
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
// or implied. See the License for the specific language governing permissions and limitations under the License.

#include <faiss/IndexPreTransform.h>
#include <faiss/IndexRaBitQ.h>
#include <faiss/cppcontrib/knowhere/IndexBinaryScalarQuantizer.h>
#include <faiss/cppcontrib/knowhere/IndexCosine.h>
#include <faiss/cppcontrib/knowhere/IndexFlat.h>
#include <faiss/cppcontrib/knowhere/IndexHNSWBinary.h>
#include <faiss/cppcontrib/knowhere/IndexHNSWRaBitQ.h>
#include <faiss/cppcontrib/knowhere/IndexSQ4Uniform.h>
#include <faiss/cppcontrib/knowhere/MetricType.h>
#include <faiss/cppcontrib/knowhere/impl/CountSizeIOWriter.h>
Expand Down Expand Up @@ -672,31 +675,41 @@ convert_ds_to_float(const DataSetPtr& src, DataFormatEnum data_format) {
}

Status
add_to_index(faiss::Index* const __restrict index, const DataSetPtr& dataset, const DataFormatEnum data_format) {
add_to_index(faiss::Index* const __restrict index, const DataSetPtr& dataset, const DataFormatEnum data_format,
bool chunk_fp32 = false) {
const auto* data = dataset->GetTensor();
const auto rows = dataset->GetRows();
const auto dim = dataset->GetDim();

if (data_format == DataFormatEnum::fp32) {
if (data_format == DataFormatEnum::fp32 && !chunk_fp32) {
// add as is
index->add(rows, reinterpret_cast<const float*>(data));
} else {
// convert data into float in pieces and add to the index
constexpr int64_t n_tmp_rows = 4096;
std::unique_ptr<float[]> tmp = std::make_unique<float[]>(n_tmp_rows * dim);
std::unique_ptr<float[]> tmp;
if (data_format != DataFormatEnum::fp32) {
tmp = std::make_unique<float[]>(n_tmp_rows * dim);
}

for (int64_t irow = 0; irow < rows; irow += n_tmp_rows) {
const int64_t start_row = irow;
const int64_t end_row = std::min(rows, start_row + n_tmp_rows);
const int64_t count_rows = end_row - start_row;

if (!convert_rows_to_fp32(data, tmp.get(), data_format, start_row, count_rows, dim)) {
LOG_KNOWHERE_ERROR_ << "Unsupported data format";
return Status::invalid_args;
const float* chunk = nullptr;
if (data_format == DataFormatEnum::fp32) {
chunk = reinterpret_cast<const float*>(data) + start_row * dim;
} else {
if (!convert_rows_to_fp32(data, tmp.get(), data_format, start_row, count_rows, dim)) {
LOG_KNOWHERE_ERROR_ << "Unsupported data format";
return Status::invalid_args;
}
chunk = tmp.get();
}

// add
index->add(count_rows, tmp.get());
index->add(count_rows, chunk);
}
}

Expand Down Expand Up @@ -3032,6 +3045,235 @@ class BaseFaissRegularIndexHNSWPQNodeTemplate : public BaseFaissRegularIndexHNSW
}
};

// Build an exact HNSW graph with Flat storage, train RaBitQ independently,
// then replace the Flat storage after both indexes have received the data.
// RaBitQ does not currently provide the symmetric code-to-code distance that
// HNSW graph construction requires, so the finalized index is intentionally
// immutable.
class BaseFaissRegularIndexHNSWRaBitQNode : public BaseFaissRegularIndexHNSWNode {
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public:
BaseFaissRegularIndexHNSWRaBitQNode(const int32_t& version, const Object& object, DataFormatEnum data_format)
: BaseFaissRegularIndexHNSWNode(version, object, data_format) {
}

static std::unique_ptr<BaseConfig>
StaticCreateConfig() {
return std::make_unique<FaissHnswRaBitQConfig>();
}

std::unique_ptr<BaseConfig>
CreateConfig() const override {
return StaticCreateConfig();
}

std::string
Type() const override {
return knowhere::IndexEnum::INDEX_HNSW_RABITQ;
}

bool
IsAdditionalScalarSupported(bool) const override {
return false;
}

bool
IsIndexRefineEnabled() const override {
return !indexes.empty() && std::all_of(indexes.begin(), indexes.end(), [](const auto& index) {
return index != nullptr &&
dynamic_cast<const faiss::cppcontrib::knowhere::IndexRefine*>(index.get()) != nullptr;
});
}

protected:
std::vector<std::unique_ptr<faiss::IndexPreTransform>> tmp_index_rabitq;

Status
TrainInternal(const DataSetPtr dataset, const Config& cfg) override {
const auto rows = dataset->GetRows();
const auto dim = dataset->GetDim();
const auto& hnsw_cfg = static_cast<const FaissHnswRaBitQConfig&>(cfg);

auto metric = Str2FaissMetricType(hnsw_cfg.metric_type.value());
if (!metric.has_value() ||
(metric.value() != faiss::METRIC_L2 && metric.value() != faiss::METRIC_INNER_PRODUCT)) {
LOG_KNOWHERE_ERROR_ << "HNSW_RABITQ only supports L2, IP and COSINE metrics";
return Status::invalid_metric_type;
}
const bool is_cosine = IsMetricType(hnsw_cfg.metric_type.value(), metric::COSINE);
const auto& scalar_info_map =
dataset->Get<std::unordered_map<int64_t, std::vector<std::vector<uint32_t>>>>(meta::SCALAR_INFO);
if (!scalar_info_map.empty()) {
LOG_KNOWHERE_ERROR_ << "HNSW_RABITQ does not support building with scalar info";
return Status::invalid_args;
}

auto float_ds_ptr = convert_ds_to_float(dataset, data_format);
if (float_ds_ptr == nullptr) {
LOG_KNOWHERE_ERROR_ << "Unsupported data format";
return Status::invalid_args;
}
const auto* data = static_cast<const float*>(float_ds_ptr->GetTensor());

try {
std::unique_ptr<faiss::cppcontrib::knowhere::IndexHNSW> hnsw_index;
if (is_cosine) {
hnsw_index =
std::make_unique<faiss::cppcontrib::knowhere::IndexHNSWFlatCosine>(dim, hnsw_cfg.M.value());
} else {
hnsw_index = std::make_unique<faiss::cppcontrib::knowhere::IndexHNSWFlat>(dim, hnsw_cfg.M.value(),
metric.value());
}
hnsw_index->hnsw.efConstruction = hnsw_cfg.efConstruction.value();

const auto rbq_bits = static_cast<uint8_t>(hnsw_cfg.rbq_bits.value());
auto rabitq_index = std::make_unique<faiss::IndexRaBitQ>(dim, metric.value(), rbq_bits, rbq_bits > 1);
// HNSW_RABITQ V1 always uses an FP32 query.
rabitq_index->qb = 0;
rabitq_index->centered = false;
auto rotation = std::make_unique<faiss::RandomRotationMatrix>(dim, dim);
std::unique_ptr<faiss::IndexPreTransform> transformed_rabitq;
if (is_cosine) {
transformed_rabitq = std::make_unique<faiss::cppcontrib::knowhere::IndexPreTransformRaBitQCosine>(
rotation.get(), rabitq_index.get());
} else {
transformed_rabitq = std::make_unique<faiss::IndexPreTransform>(rotation.get(), rabitq_index.get());
}
transformed_rabitq->own_fields = true;
rotation.release();
rabitq_index.release();

std::unique_ptr<faiss::Index> final_index;
if (hnsw_cfg.refine.value_or(false) && hnsw_cfg.refine_type.has_value()) {
const auto hnsw_d = hnsw_index->storage->d;
const auto hnsw_metric_type = hnsw_index->storage->metric_type;
auto final_index_cnd = pick_refine_index(data_format, hnsw_cfg.refine_type, std::move(hnsw_index),
hnsw_d, hnsw_metric_type);
if (!final_index_cnd.has_value()) {
return Status::invalid_args;
}
final_index = std::move(final_index_cnd.value());
} else {
final_index = std::move(hnsw_index);
}

LOG_KNOWHERE_INFO_ << "Training exact HNSW graph storage";
final_index->train(rows, data);
LOG_KNOWHERE_INFO_ << "Training RaBitQ storage";
transformed_rabitq->train(rows, data);

indexes[0] = std::move(final_index);
tmp_index_rabitq.clear();
tmp_index_rabitq.emplace_back(std::move(transformed_rabitq));
} catch (const std::exception& e) {
LOG_KNOWHERE_WARNING_ << "faiss inner error: " << e.what();
return Status::faiss_inner_error;
}

return Status::success;
}

Status
AddInternal(const DataSetPtr dataset, const Config&) override {
if (isIndexEmpty()) {
LOG_KNOWHERE_ERROR_ << "Can not add data to an empty index.";
return Status::empty_index;
}
if (tmp_index_rabitq.size() != indexes.size() || tmp_index_rabitq.empty() || tmp_index_rabitq[0] == nullptr) {
LOG_KNOWHERE_ERROR_ << "HNSW_RABITQ is immutable after its initial Add";
return Status::not_implemented;
}

const auto& scalar_info_map =
dataset->Get<std::unordered_map<int64_t, std::vector<std::vector<uint32_t>>>>(meta::SCALAR_INFO);
if (!scalar_info_map.empty()) {
LOG_KNOWHERE_ERROR_ << "HNSW_RABITQ does not support building with scalar info";
return Status::invalid_args;
}

try {
LOG_KNOWHERE_INFO_ << "Adding " << dataset->GetRows() << " rows to exact HNSW graph";
auto status = add_to_index(indexes[0].get(), dataset, data_format);
if (status != Status::success) {
return status;
}

LOG_KNOWHERE_INFO_ << "Adding " << dataset->GetRows() << " rows to RaBitQ storage";
// IndexPreTransform materializes its transformed input. Bound that
// temporary allocation instead of rotating the full FP32 dataset
// in one call.
status = add_to_index(tmp_index_rabitq[0].get(), dataset, data_format, true);
if (status != Status::success) {
return status;
}

faiss::cppcontrib::knowhere::IndexRefine* index_refine =
dynamic_cast<faiss::cppcontrib::knowhere::IndexRefine*>(indexes[0].get());
auto* index_hnsw = index_refine != nullptr
? dynamic_cast<faiss::cppcontrib::knowhere::IndexHNSW*>(index_refine->base_index)
: dynamic_cast<faiss::cppcontrib::knowhere::IndexHNSW*>(indexes[0].get());
if (index_hnsw == nullptr) {
LOG_KNOWHERE_ERROR_ << "HNSW_RABITQ build produced an unexpected base index";
return Status::invalid_index_error;
}

const bool is_cosine = faiss::cppcontrib::knowhere::is_cosine_index(index_hnsw->storage);
std::unique_ptr<faiss::cppcontrib::knowhere::IndexHNSWRaBitQ> index_hnsw_rabitq;
if (is_cosine) {
index_hnsw_rabitq = std::make_unique<faiss::cppcontrib::knowhere::IndexHNSWRaBitQCosine>();
} else {
index_hnsw_rabitq = std::make_unique<faiss::cppcontrib::knowhere::IndexHNSWRaBitQ>();
}
// C++ slicing is intentional: preserve the exact graph while
// changing only the runtime HNSW type and its vector storage.
static_cast<faiss::cppcontrib::knowhere::IndexHNSW&>(*index_hnsw_rabitq) =
static_cast<faiss::cppcontrib::knowhere::IndexHNSW&>(*index_hnsw);

// Validate the replacement before relinquishing either owner so a
// malformed storage cannot leave the exact graph half-finalized.
auto* flat_storage = index_hnsw->storage;
index_hnsw_rabitq->storage = tmp_index_rabitq[0].get();
index_hnsw_rabitq->own_fields = false;
if (is_cosine) {
dynamic_cast<faiss::cppcontrib::knowhere::IndexHNSWRaBitQCosine*>(index_hnsw_rabitq.get())
->validate_cosine_storage();
} else {
index_hnsw_rabitq->validate_storage();
}
index_hnsw_rabitq->own_fields = true;
tmp_index_rabitq[0].release();
index_hnsw->storage = nullptr;
delete flat_storage;

if (index_refine != nullptr) {
delete index_refine->base_index;
index_refine->base_index = index_hnsw_rabitq.release();
} else {
indexes[0] = std::move(index_hnsw_rabitq);
}
tmp_index_rabitq.clear();
} catch (const std::exception& e) {
LOG_KNOWHERE_WARNING_ << "faiss inner error: " << e.what();
return Status::faiss_inner_error;
}

return Status::success;
}
};

template <typename DataType>
class BaseFaissRegularIndexHNSWRaBitQNodeTemplate : public BaseFaissRegularIndexHNSWRaBitQNode {
public:
BaseFaissRegularIndexHNSWRaBitQNodeTemplate(const int32_t& version, const Object& object)
: BaseFaissRegularIndexHNSWRaBitQNode(version, object, datatype_v<DataType>) {
}

static bool
StaticHasRawData(const knowhere::BaseConfig& config, const IndexVersion& version) {
const auto& hnsw_cfg = static_cast<const FaissHnswRaBitQConfig&>(config);
return has_lossless_refine_index(hnsw_cfg.refine, hnsw_cfg.refine_type, datatype_v<DataType>);
}
};

// this index trains PRQ and HNSW+FLAT separately, then constructs HNSW+PRQ
class BaseFaissRegularIndexHNSWPRQNode : public BaseFaissRegularIndexHNSWNode {
public:
Expand Down Expand Up @@ -3354,5 +3596,7 @@ KNOWHERE_SIMPLE_REGISTER_DENSE_FLOAT_ALL_GLOBAL(HNSW_PRQ, BaseFaissRegularIndexH
knowhere::feature::EMB_LIST)
KNOWHERE_SIMPLE_REGISTER_DENSE_INT_GLOBAL(HNSW_PRQ, BaseFaissRegularIndexHNSWPRQNodeTemplate,
knowhere::feature::MMAP | knowhere::feature::MV | knowhere::feature::EMB_LIST)
KNOWHERE_SIMPLE_REGISTER_DENSE_FLOAT_ALL_GLOBAL(HNSW_RABITQ, BaseFaissRegularIndexHNSWRaBitQNodeTemplate,
knowhere::feature::NONE)

} // namespace knowhere
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