Global HNSW vector index

Author: mkaruza

src/core/search/ast_expr.cc

@@ -73,6 +73,10 @@ AstKnnNode::AstKnnNode(AstNode&& filter, AstKnnNode&& self) {
   this->filter = make_unique<AstNode>(std::move(filter));
 }
 
+bool AstKnnNode::PreFilter() const {
+  return filter == nullptr;
+}
+
 }  // namespace dfly::search
 
 namespace std {

src/core/search/ast_expr.h

@@ -114,6 +114,8 @@ struct AstKnnNode {
   OwnedFtVector vec;
   std::string score_alias;
   std::optional<float> ef_runtime;
+
+  bool PreFilter() const;
 };
 
 using NodeVariants =

src/core/search/base.h

@@ -16,10 +16,24 @@
 #include "absl/container/flat_hash_set.h"
 #include "base/pmr/memory_resource.h"
 #include "core/string_map.h"
+#include "server/tx_base.h"
 
 namespace dfly::search {
 
 using DocId = uint32_t;
+using GlobalDocId = uint64_t;
+
+inline GlobalDocId CreateGlobalDocId(ShardId shard_id, DocId local_doc_id) {
+  return ((uint64_t)shard_id << 32) | local_doc_id;
+}
+
+inline ShardId GlobalDocIdShardId(GlobalDocId id) {
+  return (id >> 32);
+}
+
+inline search::DocId GlobalDocIdLocalId(GlobalDocId id) {
+  return (id)&0xFFFF;
+}
 
 enum class VectorSimilarity { L2, IP, COSINE };
 

src/core/search/indices.cc

@@ -492,40 +492,36 @@ bool BaseVectorIndex<T>::Add(T id, const DocumentAccessor& doc, std::string_view
   return true;
 }
 
-template <typename T>
-FlatVectorIndex<T>::FlatVectorIndex(const SchemaField::VectorParams& params,
-                                    PMR_NS::memory_resource* mr)
-    : BaseVectorIndex<T>{params.dim, params.sim}, entries_{mr} {
+FlatVectorIndex::FlatVectorIndex(const SchemaField::VectorParams& params,
+                                 PMR_NS::memory_resource* mr)
+    : BaseVectorIndex<DocId>{params.dim, params.sim}, entries_{mr} {
   DCHECK(!params.use_hnsw);
   entries_.reserve(params.capacity * params.dim);
 }
 
-template <typename T>
-void FlatVectorIndex<T>::AddVector(T id, const typename BaseVectorIndex<T>::VectorPtr& vector) {
-  DCHECK_LE(id * BaseVectorIndex<T>::dim_, entries_.size());
-  if (id * BaseVectorIndex<T>::dim_ == entries_.size())
-    entries_.resize((id + 1) * BaseVectorIndex<T>::dim_);
+void FlatVectorIndex::AddVector(DocId id, const typename BaseVectorIndex::VectorPtr& vector) {
+  DCHECK_LE(id * dim_, entries_.size());
+  if (id * dim_ == entries_.size())
+    entries_.resize((id + 1) * dim_);
 
   // TODO: Let get vector write to buf itself
   if (vector) {
-    memcpy(&entries_[id * BaseVectorIndex<T>::dim_], vector.get(),
-           BaseVectorIndex<T>::dim_ * sizeof(float));
+    memcpy(&entries_[id * dim_], vector.get(), dim_ * sizeof(float));
   }
 }
 
-template <typename T>
-void FlatVectorIndex<T>::Remove(T id, const DocumentAccessor& doc, string_view field) {
+void FlatVectorIndex::Remove(DocId id, const DocumentAccessor& doc, string_view field) {
   // noop
 }
 
-template <typename T> const float* FlatVectorIndex<T>::Get(T doc) const {
+const float* FlatVectorIndex::Get(DocId doc) const {
   return &entries_[doc * dim_];
 }
 
-template <typename T> std::vector<T> FlatVectorIndex<T>::GetAllDocsWithNonNullValues() const {
+std::vector<DocId> FlatVectorIndex::GetAllDocsWithNonNullValues() const {
   std::vector<DocId> result;
 
-  size_t num_vectors = entries_.size() / BaseVectorIndex<T>::dim_;
+  size_t num_vectors = entries_.size() / dim_;
   result.reserve(num_vectors);
 
   for (DocId id = 0; id < num_vectors; ++id) {
@@ -535,7 +531,7 @@ template <typename T> std::vector<T> FlatVectorIndex<T>::GetAllDocsWithNonNullVa
     bool is_zero_vector = true;
 
     // TODO: Consider don't use check for zero vector
-    for (size_t i = 0; i < BaseVectorIndex<T>::dim_; ++i) {
+    for (size_t i = 0; i < dim_; ++i) {
       if (vec[i] != 0.0f) {  // TODO: Consider using a threshold for float comparison
         is_zero_vector = false;
         break;
@@ -552,9 +548,7 @@ template <typename T> std::vector<T> FlatVectorIndex<T>::GetAllDocsWithNonNullVa
   return result;
 }
 
-template struct FlatVectorIndex<DocId>;
-
-struct HnswlibAdapter {
+template <typename T> struct HnswlibAdapter {
   // Default setting of hnswlib/hnswalg
   constexpr static size_t kDefaultEfRuntime = 10;
 
@@ -564,34 +558,45 @@ struct HnswlibAdapter {
                100 /* seed*/} {
   }
 
-  void Add(const float* data, DocId id) {
-    if (world_.cur_element_count + 1 >= world_.max_elements_)
-      world_.resizeIndex(world_.cur_element_count * 2);
-    world_.addPoint(data, id);
+  void Add(const float* data, T id) {
+    while (true) {
+      try {
+        absl::ReaderMutexLock lock(&resize_mutex_);
+        world_.addPoint(data, id);
+        return;
+      } catch (const std::exception& e) {
+        std::string error_msg = e.what();
+        if (absl::StrContains(error_msg, "The number of elements exceeds the specified limit")) {
+          ResizeIfFull();
+          continue;
+        }
+        throw e;
+      }
+    }
   }
 
-  void Remove(DocId id) {
+  void Remove(T id) {
     try {
       world_.markDelete(id);
     } catch (const std::exception& e) {
     }
   }
 
-  vector<pair<float, DocId>> Knn(float* target, size_t k, std::optional<size_t> ef) {
+  vector<pair<float, T>> Knn(float* target, size_t k, std::optional<size_t> ef) {
     world_.setEf(ef.value_or(kDefaultEfRuntime));
     return QueueToVec(world_.searchKnn(target, k));
   }
 
-  vector<pair<float, DocId>> Knn(float* target, size_t k, std::optional<size_t> ef,
-                                 const vector<DocId>& allowed) {
+  vector<pair<float, T>> Knn(float* target, size_t k, std::optional<size_t> ef,
+                             const vector<T>& allowed) {
     struct BinsearchFilter : hnswlib::BaseFilterFunctor {
       virtual bool operator()(hnswlib::labeltype id) {
         return binary_search(allowed->begin(), allowed->end(), id);
       }
 
-      BinsearchFilter(const vector<DocId>* allowed) : allowed{allowed} {
+      BinsearchFilter(const vector<T>* allowed) : allowed{allowed} {
       }
-      const vector<DocId>* allowed;
+      const vector<T>* allowed;
     };
 
     world_.setEf(ef.value_or(kDefaultEfRuntime));
@@ -613,8 +618,30 @@ struct HnswlibAdapter {
     return visit([](auto& space) -> hnswlib::SpaceInterface<float>* { return &space; }, space_);
   }
 
-  template <typename Q> static vector<pair<float, DocId>> QueueToVec(Q queue) {
-    vector<pair<float, DocId>> out(queue.size());
+  void ResizeIfFull() {
+    {
+      absl::ReaderMutexLock lock(&resize_mutex_);
+      if (world_.getCurrentElementCount() < world_.getMaxElements() ||
+          (world_.allow_replace_deleted_ && world_.getDeletedCount() > 0)) {
+        return;
+      }
+    }
+    try {
+      absl::WriterMutexLock lock(&resize_mutex_);
+      if (world_.getCurrentElementCount() == world_.getMaxElements() &&
+          (!world_.allow_replace_deleted_ || world_.getDeletedCount() == 0)) {
+        auto max_elements = world_.getMaxElements();
+        world_.resizeIndex(max_elements * 2);
+        LOG(INFO) << "Resizing HNSW Index, current size: " << max_elements
+                  << ", expand by: " << max_elements * 2;
+      }
+    } catch (const std::exception& e) {
+      throw e;
+    }
+  }
+
+  template <typename Q> static vector<pair<float, GlobalDocId>> QueueToVec(Q queue) {
+    vector<pair<float, GlobalDocId>> out(queue.size());
     size_t idx = out.size();
     while (!queue.empty()) {
       out[--idx] = queue.top();
@@ -625,45 +652,46 @@ struct HnswlibAdapter {
 
   SpaceUnion space_;
   hnswlib::HierarchicalNSW<float> world_;
+  absl::Mutex resize_mutex_;
 };
 
-template <typename T>
-HnswVectorIndex<T>::HnswVectorIndex(const SchemaField::VectorParams& params,
-                                    PMR_NS::memory_resource*)
-    : BaseVectorIndex<T>{params.dim, params.sim}, adapter_{make_unique<HnswlibAdapter>(params)} {
+HnswVectorIndexShardPlaceholder::HnswVectorIndexShardPlaceholder(
+    const SchemaField::VectorParams& params)
+    : BaseVectorIndex<DocId>{params.dim, params.sim} {
+}
+
+HnswVectorIndex::HnswVectorIndex(const SchemaField::VectorParams& params, PMR_NS::memory_resource*)
+    : BaseVectorIndex<GlobalDocId>{params.dim, params.sim},
+      adapter_{make_unique<HnswlibAdapter<GlobalDocId>>(params)} {
   DCHECK(params.use_hnsw);
   // TODO: Patch hnsw to use MR
 }
-template <typename T> HnswVectorIndex<T>::~HnswVectorIndex() {
+
+HnswVectorIndex::~HnswVectorIndex() {
 }
 
-template <typename T>
-void HnswVectorIndex<T>::AddVector(T id, const typename BaseVectorIndex<T>::VectorPtr& vector) {
+void HnswVectorIndex::AddVector(GlobalDocId id,
+                                const typename BaseVectorIndex<GlobalDocId>::VectorPtr& vector) {
   if (vector) {
     adapter_->Add(vector.get(), id);
   }
 }
 
-template <typename T>
-std::vector<std::pair<float, T>> HnswVectorIndex<T>::Knn(float* target, size_t k,
-                                                         std::optional<size_t> ef) const {
+std::vector<std::pair<float, GlobalDocId>> HnswVectorIndex::Knn(float* target, size_t k,
+                                                                std::optional<size_t> ef) const {
   return adapter_->Knn(target, k, ef);
 }
 
-template <typename T>
-std::vector<std::pair<float, T>> HnswVectorIndex<T>::Knn(float* target, size_t k,
-                                                         std::optional<size_t> ef,
-                                                         const std::vector<T>& allowed) const {
+std::vector<std::pair<float, GlobalDocId>> HnswVectorIndex::Knn(
+    float* target, size_t k, std::optional<size_t> ef,
+    const std::vector<GlobalDocId>& allowed) const {
   return adapter_->Knn(target, k, ef, allowed);
 }
 
-template <typename T>
-void HnswVectorIndex<T>::Remove(T id, const DocumentAccessor& doc, string_view field) {
+void HnswVectorIndex::Remove(GlobalDocId id, const DocumentAccessor& doc, string_view field) {
   adapter_->Remove(id);
 }
 
-template struct HnswVectorIndex<DocId>;
-
 GeoIndex::GeoIndex(PMR_NS::memory_resource* mr) : rtree_(make_unique<rtree>()) {
 }
 

src/core/search/indices.h

@@ -175,53 +175,70 @@ template <typename T> struct BaseVectorIndex : public BaseIndex<T> {
 };
 
 // Index for vector fields.
-// Only supports lookup by id.
-template <typename T> struct FlatVectorIndex : public BaseVectorIndex<T> {
+// Only supports lookup by id.WW
+struct FlatVectorIndex : public BaseVectorIndex<DocId> {
   FlatVectorIndex(const SchemaField::VectorParams& params, PMR_NS::memory_resource* mr);
 
-  void Remove(T id, const DocumentAccessor& doc, std::string_view field) override;
+  void Remove(DocId id, const DocumentAccessor& doc, std::string_view field) override;
 
-  const float* Get(T doc) const;
+  std::vector<std::pair<float, DocId>> Knn(float* target, size_t k) const;
 
-  // Return all documents that have vectors in this index
-  std::vector<T> GetAllDocsWithNonNullValues() const override;
+  const float* Get(DocId doc) const;
+
+  std::vector<DocId> GetAllDocsWithNonNullValues() const override;
 
  protected:
-  using BaseVectorIndex<T>::dim_;
-  void AddVector(T id, const typename BaseVectorIndex<T>::VectorPtr& vector) override;
+  using BaseVectorIndex<DocId>::dim_;
+  void AddVector(DocId id, const typename BaseVectorIndex<DocId>::VectorPtr& vector) override;
 
  private:
   PMR_NS::vector<float> entries_;
 };
 
-extern template struct FlatVectorIndex<DocId>;
+struct HnswVectorIndexShardPlaceholder : public BaseVectorIndex<DocId> {
+  explicit HnswVectorIndexShardPlaceholder(const SchemaField::VectorParams& params);
 
-struct HnswlibAdapter;
+  void Remove(DocId id, const DocumentAccessor& doc, std::string_view field) override {
+    // noop
+  }
 
-template <typename T> struct HnswVectorIndex : public BaseVectorIndex<T> {
+  // Return all documents that have vectors in this index
+  std::vector<DocId> GetAllDocsWithNonNullValues() const override {
+    return {};
+  }
+
+ protected:
+  using BaseVectorIndex<DocId>::dim_;
+  void AddVector(DocId id, const typename BaseVectorIndex<DocId>::VectorPtr& vector) override {
+    // noop
+  }
+};
+
+template <typename T> struct HnswlibAdapter;
+struct HnswVectorIndex : public BaseVectorIndex<GlobalDocId> {
   HnswVectorIndex(const SchemaField::VectorParams& params, PMR_NS::memory_resource* mr);
   ~HnswVectorIndex();
 
-  void Remove(T id, const DocumentAccessor& doc, std::string_view field) override;
+  void Remove(GlobalDocId id, const DocumentAccessor& doc, std::string_view field) override;
 
-  std::vector<std::pair<float, T>> Knn(float* target, size_t k, std::optional<size_t> ef) const;
-  std::vector<std::pair<float, T>> Knn(float* target, size_t k, std::optional<size_t> ef,
-                                       const std::vector<T>& allowed) const;
+  std::vector<std::pair<float, GlobalDocId>> Knn(float* target, size_t k,
+                                                 std::optional<size_t> ef) const;
+  std::vector<std::pair<float, GlobalDocId>> Knn(float* target, size_t k, std::optional<size_t> ef,
+                                                 const std::vector<GlobalDocId>& allowed) const;
 
   // TODO: Implement if needed
-  std::vector<T> GetAllDocsWithNonNullValues() const override {
-    return std::vector<T>{};
+  std::vector<GlobalDocId> GetAllDocsWithNonNullValues() const override {
+    return std::vector<GlobalDocId>{};
   }
 
  protected:
-  void AddVector(T id, const typename BaseVectorIndex<T>::VectorPtr& vector) override;
+  void AddVector(GlobalDocId id,
+                 const typename BaseVectorIndex<GlobalDocId>::VectorPtr& vector) override;
 
  private:
-  std::unique_ptr<HnswlibAdapter> adapter_;
+  std::unique_ptr<HnswlibAdapter<GlobalDocId>> adapter_;
 };
 
-extern template struct HnswVectorIndex<DocId>;
-
 struct GeoIndex : public BaseIndex<DocId> {
   using point =
       boost::geometry::model::point<double, 2,