Use RemoteCreateVertex in CreateNode operator

Summary:
- Add `database::GraphDb::GetWorkerIds()`
- Change `CreateNode` constructor API
- Make `CreateNode` distribute nodes uniformly over workers

Did not yet modify `CreateExpand`, coming in the next diff.

Reviewers: teon.banek

Reviewed By: teon.banek

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D1216

src/database/graph_db.cpp

@@ -99,6 +99,7 @@ class SingleNode : public PrivateBase {
   StorageGc storage_gc_{storage_, tx_engine_, config_.gc_cycle_sec};
   TypemapPack<SingleNodeConcurrentIdMapper> typemap_pack_;
   database::SingleNodeCounters counters_;
+  std::vector<int> GetWorkerIds() const override { return {0}; }
   distributed::RemoteDataRpcServer &remote_data_server() override {
     LOG(FATAL) << "Remote data server not available in single-node.";
   }
@@ -123,6 +124,9 @@ class SingleNode : public PrivateBase {
 };
 
 #define IMPL_DISTRIBUTED_GETTERS                                            \
+  std::vector<int> GetWorkerIds() const override {                          \
+    return coordination_.GetWorkerIds();                                    \
+  }                                                                         \
   distributed::RemoteDataRpcServer &remote_data_server() override {         \
     return remote_data_server_;                                             \
   }                                                                         \
@@ -251,6 +255,9 @@ ConcurrentIdMapper<Property> &PublicBase::property_mapper() {
 database::Counters &PublicBase::counters() { return impl_->counters(); }
 void PublicBase::CollectGarbage() { impl_->CollectGarbage(); }
 int PublicBase::WorkerId() const { return impl_->WorkerId(); }
+std::vector<int> PublicBase::GetWorkerIds() const {
+  return impl_->GetWorkerIds();
+}
 distributed::RemoteDataRpcServer &PublicBase::remote_data_server() {
   return impl_->remote_data_server();
 }

src/database/graph_db.hpp

@@ -2,6 +2,7 @@
 
 #include <atomic>
 #include <memory>
+#include <vector>
 
 #include "database/counters.hpp"
 #include "database/storage.hpp"
@@ -90,6 +91,7 @@ class GraphDb {
   virtual database::Counters &counters() = 0;
   virtual void CollectGarbage() = 0;
   virtual int WorkerId() const = 0;
+  virtual std::vector<int> GetWorkerIds() const = 0;
 
   // Supported only in distributed master and worker, not in single-node.
   virtual distributed::RemoteDataRpcServer &remote_data_server() = 0;
@@ -134,6 +136,7 @@ class PublicBase : public GraphDb {
   database::Counters &counters() override;
   void CollectGarbage() override;
   int WorkerId() const override;
+  std::vector<int> GetWorkerIds() const override;
   distributed::RemoteDataRpcServer &remote_data_server() override;
   distributed::RemoteDataRpcClients &remote_data_clients() override;
   distributed::PlanDispatcher &plan_dispatcher() override;

src/distributed/coordination.hpp

@@ -14,7 +14,7 @@ class Coordination {
 
   /** Gets the connected worker ids - should only be called on a master
    * instance*/
-  virtual std::vector<int> GetWorkerIds() = 0;
+  virtual std::vector<int> GetWorkerIds() const = 0;
 };
 
 }  // namespace distributed

src/distributed/coordination_master.cpp

@@ -57,7 +57,7 @@ Endpoint MasterCoordination::GetEndpoint(int worker_id) {
   return found->second;
 }
 
-std::vector<int> MasterCoordination::GetWorkerIds() {
+std::vector<int> MasterCoordination::GetWorkerIds() const {
   std::vector<int> worker_ids;
   for (auto worker : workers_) worker_ids.push_back(worker.first);
   return worker_ids;

src/distributed/coordination_master.hpp

@@ -36,7 +36,7 @@ class MasterCoordination : public Coordination {
   Endpoint GetEndpoint(int worker_id) override;
 
   /** Returns all workers id, this includes master id(0) */
-  std::vector<int> GetWorkerIds() override;
+  std::vector<int> GetWorkerIds() const override;
 
  private:
   communication::rpc::Server server_;

src/distributed/coordination_worker.cpp

@@ -54,7 +54,7 @@ void WorkerCoordination::WaitForShutdown() {
   std::this_thread::sleep_for(100ms);
 };
 
-std::vector<int> WorkerCoordination::GetWorkerIds() {
+std::vector<int> WorkerCoordination::GetWorkerIds() const {
   LOG(FATAL) << "Unimplemented worker ids discovery on worker";
 };
 }  // namespace distributed

src/distributed/coordination_worker.hpp

@@ -30,7 +30,7 @@ class WorkerCoordination : public Coordination {
 
   /** Shouldn't be called on worker for now!
    * TODO fix this */
-  std::vector<int> GetWorkerIds() override;
+  std::vector<int> GetWorkerIds() const override;
 
   /** Starts listening for a remote shutdown command (issued by the master).
    * Blocks the calling thread until that has finished. */

src/query/plan/operator.cpp

@@ -94,9 +94,11 @@ std::unique_ptr<Cursor> Once::MakeCursor(database::GraphDbAccessor &) const {
 
 void Once::OnceCursor::Reset() { did_pull_ = false; }
 
-CreateNode::CreateNode(NodeAtom *node_atom,
-                       const std::shared_ptr<LogicalOperator> &input)
-    : node_atom_(node_atom), input_(input ? input : std::make_shared<Once>()) {}
+CreateNode::CreateNode(const std::shared_ptr<LogicalOperator> &input,
+                       NodeAtom *node_atom, bool on_random_worker)
+    : input_(input ? input : std::make_shared<Once>()),
+      node_atom_(node_atom),
+      on_random_worker_(on_random_worker) {}
 
 ACCEPT_WITH_INPUT(CreateNode)
 
@@ -118,7 +120,17 @@ CreateNode::CreateNodeCursor::CreateNodeCursor(const CreateNode &self,
 
 bool CreateNode::CreateNodeCursor::Pull(Frame &frame, Context &context) {
   if (input_cursor_->Pull(frame, context)) {
-    Create(frame, context);
+    if (self_.on_random_worker_) {
+      auto worker_ids = context.db_accessor_.db().GetWorkerIds();
+      auto worker_id = worker_ids[rand_(gen_) % worker_ids.size()];
+      if (worker_id == context.db_accessor_.db().WorkerId()) {
+        CreateLocally(frame, context);
+      } else {
+        CreateOnWorker(worker_id, frame, context);
+      }
+    } else {
+      CreateLocally(frame, context);
+    }
     return true;
   }
   return false;
@@ -126,7 +138,8 @@ bool CreateNode::CreateNodeCursor::Pull(Frame &frame, Context &context) {
 
 void CreateNode::CreateNodeCursor::Reset() { input_cursor_->Reset(); }
 
-void CreateNode::CreateNodeCursor::Create(Frame &frame, Context &context) {
+void CreateNode::CreateNodeCursor::CreateLocally(Frame &frame,
+                                                 Context &context) {
   auto new_node = db_.InsertVertex();
   for (auto label : self_.node_atom_->labels_) new_node.add_label(label);
 
@@ -139,6 +152,29 @@ void CreateNode::CreateNodeCursor::Create(Frame &frame, Context &context) {
   frame[context.symbol_table_.at(*self_.node_atom_->identifier_)] = new_node;
 }
 
+void CreateNode::CreateNodeCursor::CreateOnWorker(int worker_id, Frame &frame,
+                                                  Context &context) {
+  std::unordered_map<storage::Property, query::TypedValue> properties;
+
+  // Evaluator should use the latest accessors, as modified in this query, when
+  // setting properties on new nodes.
+  ExpressionEvaluator evaluator(frame, context.parameters_,
+                                context.symbol_table_, db_, GraphView::NEW);
+  for (auto &kv : self_.node_atom_->properties_) {
+    auto value = kv.second->Accept(evaluator);
+    if (!value.IsPropertyValue()) {
+      throw QueryRuntimeException("'{}' cannot be used as a property value.",
+                                  value.type());
+    }
+    properties.emplace(kv.first.second, std::move(value));
+  }
+
+  auto new_node = context.db_accessor_.InsertVertexIntoRemote(
+      worker_id, self_.node_atom_->labels_, properties);
+
+  frame[context.symbol_table_.at(*self_.node_atom_->identifier_)] = new_node;
+}
+
 CreateExpand::CreateExpand(NodeAtom *node_atom, EdgeAtom *edge_atom,
                            const std::shared_ptr<LogicalOperator> &input,
                            Symbol input_symbol, bool existing_node)
@@ -349,10 +385,10 @@ std::unique_ptr<Cursor> ScanAllByLabelPropertyRange::MakeCursor(
                                   context.symbol_table_, db, graph_view_);
     auto convert = [&evaluator](const auto &bound)
         -> std::experimental::optional<utils::Bound<PropertyValue>> {
-          if (!bound) return std::experimental::nullopt;
-          return std::experimental::make_optional(utils::Bound<PropertyValue>(
-              bound.value().value()->Accept(evaluator), bound.value().type()));
-        };
+      if (!bound) return std::experimental::nullopt;
+      return std::experimental::make_optional(utils::Bound<PropertyValue>(
+          bound.value().value()->Accept(evaluator), bound.value().type()));
+    };
     return db.Vertices(label_, property_, convert(lower_bound()),
                        convert(upper_bound()), graph_view_ == GraphView::NEW);
   };
@@ -1894,7 +1930,7 @@ bool ExpandUniquenessFilter<TAccessor>::ExpandUniquenessFilterCursor::Pull(
     for (const auto &previous_symbol : self_.previous_symbols_) {
       TypedValue &previous_value = frame[previous_symbol];
       // This shouldn't raise a TypedValueException, because the planner
-      // makes sure these are all of the expected type. In case they are not,
+      // makes sure these are all of the expected type. In case they are not
       // an error should be raised long before this code is executed.
       if (ContainsSame<TAccessor>(previous_value, expand_value)) return false;
     }

src/query/plan/operator.hpp

@@ -4,6 +4,7 @@
 
 #include <experimental/optional>
 #include <memory>
+#include <random>
 #include <unordered_map>
 #include <unordered_set>
 #include <utility>
@@ -237,15 +238,16 @@ class Once : public LogicalOperator {
 class CreateNode : public LogicalOperator {
  public:
   /**
-   *
-   * @param node_atom @c NodeAtom with information on how to create a node.
    * @param input Optional. If @c nullptr, then a single node will be
    *    created (a single successful @c Cursor::Pull from this op's @c Cursor).
    *    If a valid input, then a node will be created for each
    *    successful pull from the given input.
+   * @param node_atom @c NodeAtom with information on how to create a node.
+   * @param on_random_worker If the node should be created locally or on random
+   * worker.
    */
-  CreateNode(NodeAtom *node_atom,
-             const std::shared_ptr<LogicalOperator> &input);
+  CreateNode(const std::shared_ptr<LogicalOperator> &input, NodeAtom *node_atom,
+             bool on_random_worker);
   bool Accept(HierarchicalLogicalOperatorVisitor &visitor) override;
   std::unique_ptr<Cursor> MakeCursor(
       database::GraphDbAccessor &db) const override;
@@ -257,8 +259,9 @@ class CreateNode : public LogicalOperator {
  private:
   CreateNode() {}
 
-  NodeAtom *node_atom_ = nullptr;
   std::shared_ptr<LogicalOperator> input_;
+  NodeAtom *node_atom_ = nullptr;
+  bool on_random_worker_;
 
   class CreateNodeCursor : public Cursor {
    public:
@@ -271,10 +274,15 @@ class CreateNode : public LogicalOperator {
     database::GraphDbAccessor &db_;
     const std::unique_ptr<Cursor> input_cursor_;
 
-    /**
-     * Creates a single node and places it in the frame.
-     */
-    void Create(Frame &, Context &);
+    // For random worker choosing in distributed.
+    std::mt19937 gen_{std::random_device{}()};
+    std::uniform_int_distribution<int> rand_;
+
+    /** Creates a single node locally and places it in the frame. */
+    void CreateLocally(Frame &, Context &);
+
+    /** Creates a single node on the given worker and places it in the frame. */
+    void CreateOnWorker(int worker_id, Frame &, Context &);
   };
 
   friend class boost::serialization::access;
@@ -286,6 +294,7 @@ class CreateNode : public LogicalOperator {
     ar &boost::serialization::base_object<LogicalOperator>(*this);
     ar &input_;
     SavePointer(ar, node_atom_);
+    ar &on_random_worker_;
   }
 
   template <class TArchive>
@@ -293,6 +302,7 @@ class CreateNode : public LogicalOperator {
     ar &boost::serialization::base_object<LogicalOperator>(*this);
     ar &input_;
     LoadPointer(ar, node_atom_);
+    ar &on_random_worker_;
   }
 };
 

src/query/plan/rule_based_planner.cpp

@@ -595,7 +595,7 @@ std::unique_ptr<LogicalOperator> GenCreateForPattern(
     std::unordered_set<Symbol> &bound_symbols) {
   auto base = [&](NodeAtom *node) -> std::unique_ptr<LogicalOperator> {
     if (bound_symbols.insert(symbol_table.at(*node->identifier_)).second)
-      return std::make_unique<CreateNode>(node, std::move(input_op));
+      return std::make_unique<CreateNode>(std::move(input_op), node, false);
     else
       return std::move(input_op);
   };

tests/unit/distributed_graph_db.cpp

@@ -388,3 +388,31 @@ TEST_F(DistributedGraphDbTest, Synchronize) {
 
   // TODO test without advance command?
 }
+
+TEST_F(DistributedGraphDbTest, Create) {
+  // Query: UNWIND range(0, 1000) as x CREATE ()
+  auto &db = master();
+  GraphDbAccessor dba{db};
+  Context ctx{dba};
+  SymbolGenerator symbol_generator{ctx.symbol_table_};
+  AstTreeStorage storage;
+  auto range = FN("range", LITERAL(0), LITERAL(1000));
+  auto x = ctx.symbol_table_.CreateSymbol("x", true);
+  auto unwind = std::make_shared<plan::Unwind>(nullptr, range, x);
+  auto node = NODE("n");
+  ctx.symbol_table_[*node->identifier_] =
+      ctx.symbol_table_.CreateSymbol("n", true);
+  auto create = std::make_shared<query::plan::CreateNode>(unwind, node, true);
+  PullAll(create, dba, ctx.symbol_table_);
+  dba.Commit();
+
+  auto vertex_count = [](database::GraphDb &db) {
+    database::GraphDbAccessor dba{db};
+    auto vertices = dba.Vertices(false);
+    return std::distance(vertices.begin(), vertices.end());
+  };
+
+  EXPECT_GT(vertex_count(master()), 200);
+  EXPECT_GT(vertex_count(worker(1)), 200);
+  EXPECT_GT(vertex_count(worker(2)), 200);
+}

tests/unit/query_plan_accumulate_aggregate.cpp

@@ -94,7 +94,7 @@ TEST(QueryPlan, AccumulateAdvance) {
     auto node = NODE("n");
     auto sym_n = symbol_table.CreateSymbol("n", true);
     symbol_table[*node->identifier_] = sym_n;
-    auto create = std::make_shared<CreateNode>(node, nullptr);
+    auto create = std::make_shared<CreateNode>(nullptr, node, false);
     auto accumulate = std::make_shared<Accumulate>(
         create, std::vector<Symbol>{sym_n}, advance);
     auto match = MakeScanAll(storage, symbol_table, "m", accumulate);

tests/unit/query_plan_bag_semantics.cpp

@@ -95,7 +95,7 @@ TEST(QueryPlan, CreateLimit) {
   auto n = MakeScanAll(storage, symbol_table, "n1");
   auto m = NODE("m");
   symbol_table[*m->identifier_] = symbol_table.CreateSymbol("m", true);
-  auto c = std::make_shared<CreateNode>(m, n.op_);
+  auto c = std::make_shared<CreateNode>(n.op_, m, false);
   auto skip = std::make_shared<plan::Limit>(c, LITERAL(1));
 
   EXPECT_EQ(1, PullAll(skip, dba, symbol_table));

tests/unit/query_plan_create_set_remove_delete.cpp

@@ -1,8 +1,3 @@
-//
-// Copyright 2017 Memgraph
-// Created by Florijan Stamenkovic on 14.03.17.
-//
-
 #include <iterator>
 #include <memory>
 #include <vector>
@@ -36,7 +31,7 @@ TEST(QueryPlan, CreateNodeWithAttributes) {
   node->labels_.emplace_back(label);
   node->properties_[property] = LITERAL(42);
 
-  auto create = std::make_shared<CreateNode>(node, nullptr);
+  auto create = std::make_shared<CreateNode>(nullptr, node, false);
   PullAll(create, dba, symbol_table);
   dba.AdvanceCommand();
 
@@ -71,7 +66,7 @@ TEST(QueryPlan, CreateReturn) {
   node->labels_.emplace_back(label);
   node->properties_[property] = LITERAL(42);
 
-  auto create = std::make_shared<CreateNode>(node, nullptr);
+  auto create = std::make_shared<CreateNode>(nullptr, node, false);
   auto named_expr_n = NEXPR("n", IDENT("n"));
   symbol_table[*named_expr_n] = symbol_table.CreateSymbol("named_expr_n", true);
   symbol_table[*named_expr_n->expression_] = sym_n;
@@ -134,7 +129,7 @@ TEST(QueryPlan, CreateExpand) {
     r->edge_types_.emplace_back(edge_type);
     r->properties_[property] = LITERAL(3);
 
-    auto create_op = std::make_shared<CreateNode>(n, nullptr);
+    auto create_op = std::make_shared<CreateNode>(nullptr, n, false);
     auto create_expand =
         std::make_shared<CreateExpand>(m, r, create_op, n_sym, cycle);
     PullAll(create_expand, dba, symbol_table);
@@ -189,7 +184,7 @@ TEST(QueryPlan, MatchCreateNode) {
   auto m = NODE("m");
   symbol_table[*m->identifier_] = symbol_table.CreateSymbol("m", true);
   // creation op
-  auto create_node = std::make_shared<CreateNode>(m, n_scan_all.op_);
+  auto create_node = std::make_shared<CreateNode>(n_scan_all.op_, m, false);
 
   EXPECT_EQ(CountIterable(dba.Vertices(false)), 3);
   PullAll(create_node, dba, symbol_table);
@@ -846,7 +841,7 @@ TEST(QueryPlan, MergeNoInput) {
   auto node = NODE("n");
   auto sym_n = symbol_table.CreateSymbol("n", true);
   symbol_table[*node->identifier_] = sym_n;
-  auto create = std::make_shared<CreateNode>(node, nullptr);
+  auto create = std::make_shared<CreateNode>(nullptr, node, false);
   auto merge = std::make_shared<plan::Merge>(nullptr, create, create);
 
   EXPECT_EQ(0, CountIterable(dba.Vertices(false)));