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fcb8d040e8
Instead of lengthy blurbs, switch to single-line, machine-readable standardized (https://spdx.dev) license identifiers. The Linux kernel switched long ago, so there is strong precedent. Three cases are handled: AGPL-only, Apache-only, and dual licensed. For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0), reasoning that our changes are extensive enough to apply our license. The changes we applied mechanically with a script, except to licenses/README.md. Closes #9937
53 lines
2.0 KiB
C++
53 lines
2.0 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: AGPL-3.0-or-later
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*/
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#pragma once
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#include <seastar/core/iostream.hh>
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#include <seastar/core/io_priority_class.hh>
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#include "reader_permit.hh"
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#include "sstables/index_reader.hh"
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#include "sstables/shared_sstable.hh"
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#include "sstables/sstables.hh"
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#include "tracing/trace_state.hh"
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namespace sstables {
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namespace mx {
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struct partition_reversing_data_source {
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seastar::data_source the_source;
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// Underneath, the data source is iterating over the sstable file in reverse order.
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// This points to the current position of the source over the underlying sstable file;
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// either the end of partition or the beginning of some row (never in the middle of a row).
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// The reference is valid as long as the data source is alive.
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const uint64_t& current_position_in_sstable;
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};
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// Returns a single partition retrieved from an sstable data file as a sequence of buffers
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// but with the clustering order of rows reversed.
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//
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// `pos` is where the partition starts.
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// `len` is the length of the partition.
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// `ir` provides access to an index over the sstable.
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//
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// `ir.data_file_positions().end` may decrease below `current_position_in_sstable`,
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// informing us that the user wants us to skip the sequence of rows between `ir.data_file_positions().end` and `current_position_in_sstable`.
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// `ir.data_file_positions().end`, if engaged, must always point at the end of partition (pos + len) or the beginning of some row.
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// We ignore the value of `ir.data_file_positions().start`.
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//
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// We assume that `ir.current_clustered_cursor()`, if engaged, is of type `sstables::mc::bsearch_clustered_cursor*`.
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//
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// The source must be closed before destruction unless `get()` was never called.
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partition_reversing_data_source make_partition_reversing_data_source(
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const schema& s, shared_sstable sst, index_reader& ir, uint64_t pos, size_t len,
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reader_permit permit, const io_priority_class& io_priority, tracing::trace_state_ptr trace_state);
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}
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}
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