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60 lines
1.8 KiB
C++
60 lines
1.8 KiB
C++
#pragma once
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#include <common/logger_useful.h>
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#include <DataStreams/MergingSortedBlockInputStream.h>
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namespace DB
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{
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/** Merges several sorted streams into one.
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* For each group of consecutive identical values of the primary key (the columns by which the data is sorted),
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* keeps row with max `version` value.
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*/
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class ReplacingSortedBlockInputStream : public MergingSortedBlockInputStream
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{
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public:
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ReplacingSortedBlockInputStream(
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const BlockInputStreams & inputs_, const SortDescription & description_,
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const String & version_column, size_t max_block_size_, WriteBuffer * out_row_sources_buf_ = nullptr)
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: MergingSortedBlockInputStream(inputs_, description_, max_block_size_, 0, out_row_sources_buf_)
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{
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if (!version_column.empty())
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version_column_number = header.getPositionByName(version_column);
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}
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String getName() const override { return "ReplacingSorted"; }
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protected:
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/// Can return 1 more records than max_block_size.
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Block readImpl() override;
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private:
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ssize_t version_column_number = -1;
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Logger * log = &Logger::get("ReplacingSortedBlockInputStream");
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/// All data has been read.
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bool finished = false;
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/// Primary key of current row.
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RowRef current_key;
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/// Primary key of next row.
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RowRef next_key;
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/// Last row with maximum version for current primary key.
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RowRef selected_row;
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/// The position (into current_row_sources) of the row with the highest version.
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size_t max_pos = 0;
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/// Sources of rows with the current primary key.
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PODArray<RowSourcePart> current_row_sources;
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void merge(MutableColumns & merged_columns, std::priority_queue<SortCursor> & queue);
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/// Output into result the rows for current primary key.
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void insertRow(MutableColumns & merged_columns, size_t & merged_rows);
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};
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}
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