fix union bug (#5674)

src/graph/validator/SetValidator.cpp

@@ -77,11 +77,29 @@ Status SetValidator::toPlan() {
     tail_ = lValidator_->tail();
     return Status::OK();
   }
+  removeStartNode(lValidator_.get());
+  removeStartNode(rValidator_.get());
   tail_ = PassThroughNode::make(qctx_, nullptr);
   NG_RETURN_IF_ERROR(lValidator_->appendPlan(tail_));
   NG_RETURN_IF_ERROR(rValidator_->appendPlan(tail_));
   return Status::OK();
 }
 
+void SetValidator::removeStartNode(Validator* validator) {
+  if (validator->tail()->kind() != PlanNode::Kind::kStart) {
+    return;
+  }
+
+  PlanNode* node = validator->root();
+  while (node->dependencies()[0]->dependencies().size() > 0UL) {
+    node = const_cast<PlanNode*>(node->dependencies()[0]);
+  }
+  if (node->dependencies().size() == 1UL) {
+    // Remain one size for add dependency
+    node->dependencies()[0] = nullptr;
+    validator->setTail(node);
+  }
+}
+
 }  // namespace graph
 }  // namespace nebula

src/graph/validator/SetValidator.h

@@ -41,6 +41,8 @@ class SetValidator final : public Validator {
    */
   Status toPlan() override;
 
+  void removeStartNode(Validator* validator);
+
  private:
   std::unique_ptr<Validator> lValidator_;
   std::unique_ptr<Validator> rValidator_;

tests/tck/features/set/Set.feature

@@ -254,6 +254,16 @@ Feature: Set Test
       | "Manu Ginobili" | 2002             | "Spurs"      |
       | "Tony Parker"   | 1999             | "Spurs"      |
       | "Tony Parker"   | 2018             | "Hornets"    |
+    When executing query:
+      """
+      fetch prop on player 'Tony Parker' yield player.age AS age
+      UNION
+      go from 'Tim Duncan' over like yield $$.player.age AS age
+      """
+    Then the result should be, in any order:
+      | age |
+      | 36  |
+      | 41  |
 
   Scenario: Minus
     Given a graph with space named "nba"