[FEAT MERGE] [v4.2] add table generator and several random utility functions

src/sql/engine/expr/ob_expr_generator_func.h

@@ -0,0 +1,50 @@
+/**
+ * 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_SQL_OB_EXPR_FUNC_GENERATOR_FUNC_H_
+#define OCEANBASE_SQL_OB_EXPR_FUNC_GENERATOR_FUNC_H_
+
+#include "sql/engine/expr/ob_expr_operator.h"
+
+namespace oceanbase
+{
+namespace sql
+{
+class ObExprGeneratorFunc : public ObFuncExprOperator
+{
+	class ObExprGeneratorFuncCtx: public ObExprOperatorCtx
+	{
+	public:
+		ObExprGeneratorFuncCtx() : curr_value_(0) {}
+    ~ObExprGeneratorFuncCtx() = default;
+    // increment 1 after every call to expr evaluation
+    int64_t curr_value_;
+  };
+public:
+	explicit ObExprGeneratorFunc(common::ObIAllocator &alloc);
+	virtual ~ObExprGeneratorFunc();
+  virtual int calc_result_type1(ObExprResType &type,
+                                ObExprResType &limit,
+                                common::ObExprTypeCtx &type_ctx) const;
+  virtual bool need_rt_ctx() const override { return true; }
+  virtual int cg_expr(ObExprCGCtx &expr_cg_ctx,
+                      const ObRawExpr &raw_expr,
+                      ObExpr &rt_expr) const override;
+  static int eval_next_value(const ObExpr &expr, ObEvalCtx &ctx, ObDatum &res_datum);
+private:
+	DISALLOW_COPY_AND_ASSIGN(ObExprGeneratorFunc);
+};
+
+} /* namespace sql */
+} /* namespace oceanbase */
+
+#endif /* OCEANBASE_SQL_OB_EXPR_FUNC_GENERATOR_FUNC_H_ */