57 lines
2.0 KiB
C++
57 lines
2.0 KiB
C++
/**
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* Copyright (c) 2021 OceanBase
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* OceanBase CE is licensed under Mulan PubL v2.
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* You can use this software according to the terms and conditions of the Mulan PubL v2.
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* You may obtain a copy of Mulan PubL v2 at:
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* http://license.coscl.org.cn/MulanPubL-2.0
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* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
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* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
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* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
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* See the Mulan PubL v2 for more details.
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*/
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#ifndef OCEANBASE_SQL_OB_EXPR_FUNC_ZIPF_H_
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#define OCEANBASE_SQL_OB_EXPR_FUNC_ZIPF_H_
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#include <random>
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#include "sql/engine/expr/ob_expr_operator.h"
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namespace oceanbase
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{
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namespace sql
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{
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class ObExprZipf : public ObFuncExprOperator
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{
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class ObExprZipfCtx: public ObExprOperatorCtx
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{
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public:
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ObExprZipfCtx() = default;
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~ObExprZipfCtx() = default;
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int initialize(ObEvalCtx &ctx, const ObExpr &expr);
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int generate_next_value(int64_t seed, int64_t &result);
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private:
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common::ObArray<double> probe_cp_; // cumulative probability array
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std::mt19937_64 gen_; // map continuous small number to large sparse space
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};
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public:
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explicit ObExprZipf(common::ObIAllocator &alloc);
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virtual ~ObExprZipf();
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virtual int calc_result_type3(ObExprResType &result_type,
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ObExprResType &exponent,
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ObExprResType &size,
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ObExprResType &rand_expr,
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common::ObExprTypeCtx &type_ctx) const;
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virtual bool need_rt_ctx() const override { return true; }
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virtual int cg_expr(ObExprCGCtx &expr_cg_ctx,
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const ObRawExpr &raw_expr,
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ObExpr &rt_expr) const override;
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static int eval_next_value(const ObExpr &expr, ObEvalCtx &ctx, ObDatum &res_datum);
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private:
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DISALLOW_COPY_AND_ASSIGN(ObExprZipf);
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};
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} /* namespace sql */
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} /* namespace oceanbase */
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#endif /* OCEANBASE_SQL_OB_EXPR_FUNC_ZIPF_H_ */
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