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/
98 lines
2.7 KiB
C++
98 lines
2.7 KiB
C++
/*
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* Copyright (C) 2021-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
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*/
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#pragma once
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#include "mutation/tombstone.hh"
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// Merges range tombstone changes coming from different streams (readers).
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//
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// Add tombstones by calling apply().
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// Updates to the same stream identified by stream_id overwrite each other.
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// Applying an empty tombstone to a stream removes said stream.
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//
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// Call get() to get the tombstone with the highest timestamp from the currently
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// active ones.
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// Get returns disengaged optional when the last apply() call(s) didn't introduce
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// a change in the max tombstone.
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//
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// Call clear() when leaving the range abruptly (next_partition() or
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// fast_forward_to()).
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//
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// The merger doesn't keep track of the position component of the tombstones.
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// Emit them with the current position.
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template<typename stream_id_t>
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class range_tombstone_change_merger {
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struct stream_tombstone {
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stream_id_t stream_id;
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::tombstone tombstone;
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};
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private:
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std::vector<stream_tombstone> _tombstones;
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tombstone _current_tombstone;
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private:
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const stream_tombstone* get_tombstone() const {
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const stream_tombstone* max_tomb{nullptr};
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for (const auto& tomb : _tombstones) {
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if (!max_tomb || tomb.tombstone > max_tomb->tombstone) {
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max_tomb = &tomb;
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}
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}
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return max_tomb;
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}
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public:
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void apply(stream_id_t stream_id, tombstone tomb) {
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auto it = std::find_if(_tombstones.begin(), _tombstones.end(), [&] (const stream_tombstone& tomb) {
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return tomb.stream_id == stream_id;
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});
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if (it == _tombstones.end()) {
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if (tomb) {
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_tombstones.push_back({stream_id, tomb});
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}
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} else {
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if (tomb) {
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it->tombstone = tomb;
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} else {
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auto last = _tombstones.end() - 1;
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if (it != last) {
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std::swap(*it, *last);
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}
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_tombstones.pop_back();
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}
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}
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}
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std::optional<tombstone> get() {
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const auto* tomb = get_tombstone();
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if (tomb && tomb->tombstone == _current_tombstone) {
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return {};
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} else {
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_current_tombstone = tomb ? tomb->tombstone : tombstone();
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return _current_tombstone;
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}
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}
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tombstone peek() const {
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const stream_tombstone* tomb = get_tombstone();
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if (tomb) {
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return tomb->tombstone;
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} else {
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return {};
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}
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}
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void clear() {
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_tombstones.clear();
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_current_tombstone = {};
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}
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};
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