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

src/sql/engine/expr/ob_expr_uniform.h

@@ -0,0 +1,69 @@
+/**
+ * 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_UNIFORM_H_
+#define OCEANBASE_SQL_OB_EXPR_FUNC_UNIFORM_H_
+
+#include <random>
+#include "sql/engine/expr/ob_expr_operator.h"
+
+namespace oceanbase
+{
+namespace sql
+{
+class ObExprUniform : public ObFuncExprOperator
+{
+	class ObExprUniformIntCtx: public ObExprOperatorCtx
+	{
+	public:
+		ObExprUniformIntCtx() = default;
+    ~ObExprUniformIntCtx() = default;
+    int initialize(ObEvalCtx &ctx, const ObExpr &expr);
+    int generate_next_value(int64_t sample, int64_t &res);
+  private:
+    std::uniform_int_distribution<int64_t> int_dist_;
+    std::mt19937_64 gen_; // map continuous small number to large sparse space
+  };
+	class ObExprUniformRealCtx: public ObExprOperatorCtx
+	{
+	public:
+		ObExprUniformRealCtx() = default;
+    ~ObExprUniformRealCtx() = default;
+    int initialize(ObEvalCtx &ctx, const ObExpr &expr);
+    int generate_next_value(int64_t sample, double &res);
+  private:
+    std::uniform_real_distribution<double> real_dist_;
+    std::mt19937_64 gen_; // map continuous small number to large sparse space
+  };
+public:
+	explicit ObExprUniform(common::ObIAllocator &alloc);
+	virtual ~ObExprUniform();
+  virtual int calc_result_type3(ObExprResType &result_type,
+                                ObExprResType &exponent,
+                                ObExprResType &size,
+                                ObExprResType &rand_expr,
+                                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_int_value(const ObExpr &expr, ObEvalCtx &ctx, ObDatum &res_datum);
+  static int eval_next_real_value(const ObExpr &expr, ObEvalCtx &ctx, ObDatum &res_datum);
+  static int eval_next_number_value(const ObExpr &expr, ObEvalCtx &ctx, ObDatum &res_datum);
+private:
+	DISALLOW_COPY_AND_ASSIGN(ObExprUniform);
+};
+
+} /* namespace sql */
+} /* namespace oceanbase */
+
+#endif /* OCEANBASE_SQL_OB_EXPR_FUNC_UNIFORM_H_ */