AutoIndexObj primary should start with 0

mindspore/ccsrc/dataset/util/auto_index.h

@@ -91,7 +91,7 @@ class AutoIndexObj : public BPlusTree<int64_t, T, A> {
   }
 
  private:
-  static constexpr key_type kMinKey = 1;
+  static constexpr key_type kMinKey = 0;
   std::atomic<key_type> inx_;
 };
 }  // namespace dataset

tests/ut/cpp/dataset/btree_test.cc

@@ -190,9 +190,9 @@ TEST_F(MindDataTestBPlusTree, Test3) {
   EXPECT_TRUE(rc.IsOk());
   uint64_t min = ai.min_key();
   uint64_t max = ai.max_key();
-  EXPECT_EQ(min, 1);
+  EXPECT_EQ(min, 0);
-  EXPECT_EQ(max, 4);
+  EXPECT_EQ(max, 3);
-  auto r = ai.Search(3);
+  auto r = ai.Search(2);
   auto &it = r.first;
   EXPECT_EQ(it.value(), "b");
   MS_LOG(INFO) << "Dump all the values using [] operator.";