74 lines
2.3 KiB
C++
74 lines
2.3 KiB
C++
/*
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* Copyright (C) 2020 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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*
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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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#include "mutation_reader.hh"
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/*
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* Single-partition reader, a lower bound and an upper bound for the set of positions
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* of fragments returned by the reader. The bounds don't need to be exact.
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*/
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struct reader_bounds {
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flat_mutation_reader r;
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position_in_partition lower;
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position_in_partition upper;
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};
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/*
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* Returns readers from an a-priori prepared set of readers with determined lower and upper bounds
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* on the positions of their fragments.
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*/
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struct simple_position_reader_queue : public position_reader_queue {
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position_in_partition::tri_compare _cmp;
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using container_t = std::vector<reader_bounds>;
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container_t _rs;
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container_t::iterator _it;
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simple_position_reader_queue(const schema& s, std::vector<reader_bounds> rs)
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// precondition: rs sorted w.r.t lower.
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// `s` must be kept alive until the last call to `pop` or `empty`.
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: _cmp(s), _rs(std::move(rs)), _it(_rs.begin())
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{ }
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virtual ~simple_position_reader_queue() override = default;
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virtual std::vector<reader_and_upper_bound> pop(position_in_partition_view bound) override {
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if (empty(bound)) {
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return {};
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}
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// !empty(bound) implies that _it->lower <= bound.
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std::vector<reader_and_upper_bound> ret;
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auto it = _it;
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for (; it != _rs.end() && _cmp(_it->lower, it->lower) == 0; ++it) {
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ret.emplace_back(std::move(it->r), std::move(it->upper));
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}
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_it = it;
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return ret;
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}
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virtual bool empty(position_in_partition_view bound) const override {
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return _it == _rs.end() || _cmp(bound, _it->lower) < 0;
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}
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};
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