Insert vertex only (#3335)

* add insert vertex only parser

add insert vertex only validator

fix grammar

adjust insert vertex parser

* add test

* format

* merge master

* modify parser

* add fetch test

* format

* fix fetch vertex without tag error

Co-authored-by: Sophie <84560950+Sophie-Xie@users.noreply.github.com>

src/graph/planner/ngql/FetchVerticesPlanner.cpp

@@ -14,7 +14,7 @@ namespace graph {
 std::unique_ptr<FetchVerticesPlanner::VertexProps> FetchVerticesPlanner::buildVertexProps(
     const ExpressionProps::TagIDPropsMap& propsMap) {
   if (propsMap.empty()) {
-    return nullptr;
+    return std::make_unique<FetchVerticesPlanner::VertexProps>();
   }
   auto vertexProps = std::make_unique<VertexProps>(propsMap.size());
   auto fun = [](auto& tag) {

src/parser/parser.yy

@@ -2916,6 +2916,9 @@ insert_vertex_sentence
     : KW_INSERT KW_VERTEX opt_if_not_exists opt_ignore_existed_index vertex_tag_list KW_VALUES vertex_row_list {
         $$ = new InsertVerticesSentence($5, $7, $3, $4);
     }
+    | KW_INSERT KW_VERTEX opt_if_not_exists opt_ignore_existed_index KW_VALUES vertex_row_list {
+        $$ = new InsertVerticesSentence(new VertexTagList(), $6, $3, $4);
+    }
     ;
 
 vertex_tag_list

tests/tck/features/insert/insertVertexOnly.feature

@@ -0,0 +1,40 @@
+# Copyright (c) 2021 vesoft inc. All rights reserved.
+#
+# This source code is licensed under Apache 2.0 License.
+Feature: insert vertex without tag
+
+  Background: Background name
+    Given an empty graph
+    And create a space with following options:
+      | partition_num  | 9     |
+      | replica_factor | 1     |
+      | vid_type       | int64 |
+
+  Scenario: insert vertex only
+    Given having executed:
+      """
+      CREATE EDGE e();
+      """
+    And wait 6 seconds
+    When executing query:
+      """
+      INSERT VERTEX VALUES 1:(),2:(),3:();
+      INSERT EDGE e() VALUES 1->2:(),2->3:();
+      """
+    Then the execution should be successful
+    When executing query:
+      """
+      GO 2 STEP FROM 1 OVER e yield e._dst AS dst;
+      """
+    Then the result should be, in any order:
+      | dst |
+      | 3   |
+    When executing query:
+      """
+      FETCH PROP ON * 1,2 yield vertex AS v;
+      """
+    Then the result should be, in any order, with relax comparison:
+      | v   |
+      | (1) |
+      | (2) |
+    Then drop the used space