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src/sql/engine/expr/ob_expr_remove_const.h

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+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+
+#ifndef OCEANBASE_EXPR_OB_EXPR_REMOVE_CONST_H_
+#define OCEANBASE_EXPR_OB_EXPR_REMOVE_CONST_H_
+
+#include "sql/engine/expr/ob_expr_operator.h"
+namespace oceanbase {
+namespace sql {
+
+//
+// remove_const() is added above const expr to resolve the const value overwrite problem
+// in static typing engine. e.g.:
+//
+//   update t1 set (c1, c2) = (select 1, 2 from t2);
+//
+// will be rewrite to:
+//   update t1 set (c1, c2) = (select remove_const(1), remove_const(2) from t2);
+//
+//
+// remove_const(1), remove_const(2) will be overwrite when subquery is empty
+// instead of const value: 1, 2
+//
+//
+class ObExprRemoveConst : public ObFuncExprOperator {
+  public:
+  explicit ObExprRemoveConst(common::ObIAllocator& alloc);
+  virtual ~ObExprRemoveConst()
+  {}
+
+  virtual int calc_result_type1(
+      ObExprResType& type, ObExprResType& arg, common::ObExprTypeCtx& type_ctx) const override;
+
+  virtual int calc_result1(common::ObObj& result, const common::ObObj& arg, common::ObExprCtx& expr_ctx) const override;
+
+  virtual int cg_expr(ObExprCGCtx& op_cg_ctx, const ObRawExpr& raw_expr, ObExpr& rt_expr) const override;
+
+  static int eval_remove_const(const ObExpr& expr, ObEvalCtx& ctx, ObDatum& expr_datum);
+
+  private:
+  DISALLOW_COPY_AND_ASSIGN(ObExprRemoveConst);
+};
+
+}  // namespace sql
+}  // namespace oceanbase
+#endif  // OCEANBASE_EXPR_OB_EXPR_REMOVE_CONST_H_