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92 lines
2.6 KiB
C++
92 lines
2.6 KiB
C++
#pragma once
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#include <Core/Row.h>
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#include <Core/SortDescription.h>
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#include <Core/SortCursor.h>
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#include <IO/WriteHelpers.h>
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#include <DataStreams/IBlockInputStream.h>
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namespace Poco { class Logger; }
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namespace DB
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{
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/** Merges several sorted streams into one sorted stream.
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*/
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class MergingSortedBlockInputStream : public IBlockInputStream
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{
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public:
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/** limit - if isn't 0, then we can produce only first limit rows in sorted order.
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* out_row_sources - if isn't nullptr, then at the end of execution it should contain part numbers of each readed row (and needed flag)
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* quiet - don't log profiling info
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*/
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MergingSortedBlockInputStream(
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const BlockInputStreams & inputs_, SortDescription description_, size_t max_block_size_,
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UInt64 limit_ = 0, WriteBuffer * out_row_sources_buf_ = nullptr, bool quiet_ = false);
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String getName() const override { return "MergingSorted"; }
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bool isSortedOutput() const override { return true; }
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const SortDescription & getSortDescription() const override { return description; }
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Block getHeader() const override { return header; }
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protected:
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Block readImpl() override;
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void readSuffixImpl() override;
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/// Initializes the queue and the columns of next result block.
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void init(MutableColumns & merged_columns);
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/// Gets the next block from the source corresponding to the `current`.
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template <typename TSortCursor>
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void fetchNextBlock(const TSortCursor & current, SortingHeap<TSortCursor> & queue);
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Block header;
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const SortDescription description;
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const size_t max_block_size;
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UInt64 limit;
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UInt64 total_merged_rows = 0;
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bool first = true;
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bool has_collation = false;
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bool quiet = false;
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/// May be smaller or equal to max_block_size. To do 'reserve' for columns.
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size_t expected_block_size = 0;
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/// Blocks currently being merged.
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size_t num_columns = 0;
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Blocks source_blocks;
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SortCursorImpls cursors;
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SortingHeap<SortCursor> queue_without_collation;
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SortingHeap<SortCursorWithCollation> queue_with_collation;
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/// Used in Vertical merge algorithm to gather non-PK/non-index columns (on next step)
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/// If it is not nullptr then it should be populated during execution
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WriteBuffer * out_row_sources_buf;
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private:
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/** We support two different cursors - with Collation and without.
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* Templates are used instead of polymorphic SortCursor and calls to virtual functions.
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*/
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template <typename TSortingHeap>
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void merge(MutableColumns & merged_columns, TSortingHeap & queue);
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Poco::Logger * log;
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/// Read is finished.
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bool finished = false;
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};
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}
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