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9f656b96ac
When asked to upgrade a reader that itself is a downgrade, try to return the original v2 reader instead, and likewise when downgrading upgraded v1 readers. This is desirable because version transformations can result from, say, entering/leaving a reader concurrency semaphore, and the amount of such transformations is practically unbounded. Such short-circuiting is only done if it is safe, that is: the transforming reader's buffer is empty and its internal range tombstone tracking state is discardable. Signed-off-by: Michael Livshin <michael.livshin@scylladb.com>
96 lines
3.2 KiB
C++
96 lines
3.2 KiB
C++
/*
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* Copyright (C) 2021 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 <exception>
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#include <seastar/core/print.hh>
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#include "mutation_fragment_v2.hh"
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/// Converts a stream of range_tombstone_change fragments to an equivalent stream of range_tombstone objects.
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/// The input fragments must be ordered by their position().
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/// The produced range_tombstone objects are non-overlapping and ordered by their position().
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///
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/// on_end_of_stream() must be called after consuming all fragments to produce the final fragment.
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///
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/// Example usage:
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///
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/// range_tombstone_assembler rta;
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/// if (auto rt_opt = rta.consume(range_tombstone_change(...))) {
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/// produce(*rt_opt);
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/// }
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/// if (auto rt_opt = rta.consume(range_tombstone_change(...))) {
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/// produce(*rt_opt);
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/// }
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/// if (auto rt_opt = rta.flush(position_in_partition(...)) {
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/// produce(*rt_opt);
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/// }
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/// rta.on_end_of_stream();
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///
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class range_tombstone_assembler {
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std::optional<range_tombstone_change> _prev_rt;
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private:
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bool has_active_tombstone() const {
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return _prev_rt && _prev_rt->tombstone();
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}
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public:
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void reset() {
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_prev_rt = std::nullopt;
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}
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std::optional<range_tombstone> consume(const schema& s, range_tombstone_change&& rt) {
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std::optional<range_tombstone> rt_opt;
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auto less = position_in_partition::less_compare(s);
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if (has_active_tombstone() && less(_prev_rt->position(), rt.position())) {
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rt_opt = range_tombstone(_prev_rt->position(), rt.position(), _prev_rt->tombstone());
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}
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_prev_rt = std::move(rt);
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return rt_opt;
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}
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void on_end_of_stream() {
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if (has_active_tombstone()) {
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throw std::logic_error(format("Stream ends with an active range tombstone: {}", *_prev_rt));
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}
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}
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// Returns true if and only if flush() may return something.
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// Returns false if flush() won't return anything for sure.
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bool needs_flush() const {
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return has_active_tombstone();
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}
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std::optional<range_tombstone> flush(const schema& s, position_in_partition_view pos) {
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auto less = position_in_partition::less_compare(s);
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if (has_active_tombstone() && less(_prev_rt->position(), pos)) {
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position_in_partition start = _prev_rt->position();
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_prev_rt->set_position(position_in_partition(pos));
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return range_tombstone(std::move(start), pos, _prev_rt->tombstone());
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}
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return std::nullopt;
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}
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bool discardable() const {
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return !has_active_tombstone();
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}
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};
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