1c4065e7dd
This makes clear which methods of index_reader are available for use by sstable readers, and which aren't.
52 lines
1.9 KiB
C++
52 lines
1.9 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 <seastar/core/iostream.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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namespace tracing { class trace_state_ptr; }
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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, abstract_index_reader& ir, uint64_t pos, size_t len,
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reader_permit permit, tracing::trace_state_ptr trace_state);
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}
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}
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