f3eade2f62
Drop the AGPL license in favor of a source-available license. See the blog post [1] for details. [1] https://www.scylladb.com/2024/12/18/why-were-moving-to-a-source-available-license/
73 lines
2.2 KiB
C++
73 lines
2.2 KiB
C++
/*
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* Modified by ScyllaDB
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*
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* Copyright (C) 2022-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: (LicenseRef-ScyllaDB-Source-Available-1.0 and Apache-2.0)
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*/
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#pragma once
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#include "function.hh"
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#include "stateless_aggregate_function.hh"
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namespace db {
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namespace functions {
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/**
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* Performs a calculation on a set of values and return a single value.
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*/
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class aggregate_function : public virtual function {
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protected:
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stateless_aggregate_function _agg;
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private:
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shared_ptr<aggregate_function> _reducible;
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private:
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static shared_ptr<aggregate_function> make_reducible_variant(stateless_aggregate_function saf);
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public:
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explicit aggregate_function(stateless_aggregate_function saf, bool reducible_variant = false);
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/**
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* Creates a new <code>Aggregate</code> instance.
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*
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* @return a new <code>Aggregate</code> instance.
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*/
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const stateless_aggregate_function& get_aggregate() const;
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/**
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* Checks whether the function can be distributed and is able to reduce states.
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*
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* @return <code>true</code> if the function is reducible, <code>false</code> otherwise.
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*/
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bool is_reducible() const;
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/**
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* Creates a <code>Aggregate Function</code> that can be reduced.
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* Such <code>Aggregate Function</code> returns <code>Aggregate</code>,
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* which returns not finalized output, but its accumulator that can be
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* later reduced with other one.
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*
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* Reducible aggregate function can be obtained only if <code>is_reducible()</code>
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* return true. Otherwise, it should return <code>nullptr</code>.
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*
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* @return a reducible <code>Aggregate Function</code>.
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*/
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::shared_ptr<aggregate_function> reducible_aggregate_function();
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virtual const function_name& name() const override;
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virtual const std::vector<data_type>& arg_types() const override;
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virtual const data_type& return_type() const override;
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virtual bool is_pure() const override;
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virtual bool is_native() const override;
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virtual bool requires_thread() const override;
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virtual bool is_aggregate() const override;
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virtual void print(std::ostream& os) const override;
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virtual sstring column_name(const std::vector<sstring>& column_names) const override;
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};
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}
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}
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