Move input rows of Traverse and AppendVertices. (#4176)

Co-authored-by: Sophie <[email protected]>

src/graph/context/Iterator.h

@@ -73,6 +73,8 @@ class Iterator {
 
   virtual const Row* row() const = 0;
 
+  virtual Row moveRow() = 0;
+
   // erase range, no include last position, if last > size(), erase to the end
   // position
   virtual void eraseRange(size_t first, size_t last) = 0;
@@ -228,6 +230,11 @@ class DefaultIter final : public Iterator {
     return nullptr;
   }
 
+  Row moveRow() override {
+    DLOG(FATAL) << "This method should not be invoked";
+    return Row{};
+  }
+
  private:
   void doReset(size_t pos) override {
     DCHECK((pos == 0 && size() == 0) || (pos < size()));
@@ -318,6 +325,10 @@ class GetNeighborsIter final : public Iterator {
     return currentEdge_;
   }
 
+  Row moveRow() override {
+    return std::move(*currentEdge_);
+  }
+
  private:
   void doReset(size_t pos) override {
     UNUSED(pos);
@@ -475,6 +486,10 @@ class SequentialIter : public Iterator {
 
   Value getEdge() const override;
 
+  Row moveRow() override {
+    return std::move(*iter_);
+  }
+
  protected:
   const Row* row() const override {
     return &*iter_;
@@ -484,9 +499,6 @@ class SequentialIter : public Iterator {
   friend class DataCollectExecutor;
   friend class AppendVerticesExecutor;
   friend class TraverseExecutor;
-  Row&& moveRow() {
-    return std::move(*iter_);
-  }
 
   void doReset(size_t pos) override;
 

src/graph/executor/Executor.cpp

@@ -682,6 +682,27 @@ void Executor::dropBody(const PlanNode *body) {
   }
 }
 
+bool Executor::movable(const Variable *var) {
+  // Only support input variables of current executor
+  DCHECK(std::find(node_->inputVars().begin(), node_->inputVars().end(), DCHECK_NOTNULL(var)) !=
+         node_->inputVars().end());
+  // TODO support executor in loop
+  if (node()->kind() == PlanNode::Kind::kLoop) {
+    return false;
+  }
+  if (node()->loopLayers() != 0) {
+    // The lifetime of loop body is managed by Loop node
+    return false;
+  }
+
+  if (node()->kind() == PlanNode::Kind::kSelect) {
+    return false;
+  }
+  // Normal node
+  // Make sure drop happened-after count decrement
+  return var->userCount.load(std::memory_order_acquire) == 1;
+}
+
 Status Executor::finish(Result &&result) {
   if (!FLAGS_enable_lifetime_optimize ||
       node()->outputVarPtr()->userCount.load(std::memory_order_relaxed) != 0) {

src/graph/executor/Executor.h

@@ -94,6 +94,10 @@ class Executor : private boost::noncopyable, private cpp::NonMovable {
   void drop(const PlanNode *node);
   void dropBody(const PlanNode *body);
 
+  // Check whether the variable is movable, it's movable when reach end of lifetime
+  // This method shouldn't call after `finish` method!
+  bool movable(const Variable *var);
+
   // Store the result of this executor to execution context
   Status finish(Result &&result);
   // Store the default result which not used for later executor

src/graph/executor/query/AppendVerticesExecutor.cpp

@@ -101,12 +101,13 @@ Status AppendVerticesExecutor::handleResp(
   }
 
   auto *src = av->src();
+  bool mv = movable(av->inputVars().front());
   for (; inputIter->valid(); inputIter->next()) {
     auto dstFound = map.find(src->eval(ctx(inputIter.get())));
     if (dstFound == map.end()) {
       continue;
     }
-    Row row = *inputIter->row();
+    Row row = mv ? inputIter->moveRow() : *inputIter->row();
     row.values.emplace_back(dstFound->second);
     ds.rows.emplace_back(std::move(row));
   }

src/graph/executor/query/TraverseExecutor.cpp

@@ -48,6 +48,7 @@ Status TraverseExecutor::buildRequestDataSet() {
   auto* src = traverse_->src();
   QueryExpressionContext ctx(ectx_);
 
+  bool mv = movable(traverse_->inputVars().front());
   for (; iter->valid(); iter->next()) {
     auto vid = src->eval(ctx(iter));
     if (!SchemaUtil::isValidVid(vid, vidType)) {
@@ -56,7 +57,7 @@ Status TraverseExecutor::buildRequestDataSet() {
       continue;
     }
     // Need copy here, Argument executor may depends on this variable.
-    auto prePath = *iter->row();
+    auto prePath = mv ? iter->moveRow() : *iter->row();
     buildPath(prev, vid, std::move(prePath));
     if (!uniqueSet.emplace(vid).second) {
       continue;