64 lines
2.5 KiB
C++
64 lines
2.5 KiB
C++
/*
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* Copyright (C) 2019 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include "bytes.hh"
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class schema;
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class partition_key;
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class clustering_row;
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class column_computation;
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using column_computation_ptr = std::unique_ptr<column_computation>;
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/*
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* Column computation represents a computation performed in order to obtain a value for a computed column.
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* Computed columns description is also available at docs/system_schema_keyspace.md. They hold values
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* not provided directly by the user, but rather computed: from other column values and possibly other sources.
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* This class is able to serialize/deserialize column computations and perform the computation itself,
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* based on given schema, partition key and clustering row. Responsibility for providing enough data
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* in the clustering row in order for computation to succeed belongs to the caller. In particular,
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* generating a value might involve performing a read-before-write if the computation is performed
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* on more values than are present in the update request.
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*/
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class column_computation {
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public:
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virtual ~column_computation() = default;
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static column_computation_ptr deserialize(bytes_view raw);
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static column_computation_ptr deserialize(const Json::Value& json);
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virtual column_computation_ptr clone() const = 0;
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virtual bytes serialize() const = 0;
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virtual bytes_opt compute_value(const schema& schema, const partition_key& key, const clustering_row& row) const = 0;
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};
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class token_column_computation : public column_computation {
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public:
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virtual column_computation_ptr clone() const override {
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return std::make_unique<token_column_computation>(*this);
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}
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virtual bytes serialize() const override;
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virtual bytes_opt compute_value(const schema& schema, const partition_key& key, const clustering_row& row) const override;
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};
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