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85 lines
3.8 KiB
C++
85 lines
3.8 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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#include <DataStreams/ColumnGathererStream.h>
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namespace DB
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{
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/** Merges several sorted streams to 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 no more than one row with the value of the column `sign_column = -1` ("negative row")
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* and no more than a row with the value of the column `sign_column = 1` ("positive row").
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* That is, it collapses the records from the change log.
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*
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* If the number of positive and negative rows is the same, and the last row is positive, then the first negative and last positive rows are written.
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* If the number of positive and negative rows is the same, and the last line is negative, it writes nothing.
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* If the positive by 1 is greater than the negative rows, then only the last positive row is written.
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* If negative by 1 is greater than positive rows, then only the first negative row is written.
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* Otherwise, a logical error.
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*/
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class CollapsingSortedBlockInputStream : public MergingSortedBlockInputStream
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{
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public:
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CollapsingSortedBlockInputStream(
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BlockInputStreams inputs_, const SortDescription & description_,
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const String & sign_column, size_t max_block_size_,
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WriteBuffer * out_row_sources_buf_ = nullptr, bool average_block_sizes_ = false)
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: MergingSortedBlockInputStream(inputs_, description_, max_block_size_, 0, out_row_sources_buf_, false, average_block_sizes_)
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{
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sign_column_number = header.getPositionByName(sign_column);
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}
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String getName() const override { return "CollapsingSorted"; }
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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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size_t sign_column_number;
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Logger * log = &Logger::get("CollapsingSortedBlockInputStream");
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/// Read is finished.
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bool finished = false;
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SharedBlockRowRef current_key; /// The current primary key.
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SharedBlockRowRef next_key; /// The primary key of the next row.
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SharedBlockRowRef first_negative; /// The first negative row for the current primary key.
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SharedBlockRowRef last_positive; /// The last positive row for the current primary key.
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SharedBlockRowRef last_negative; /// Last negative row. It is only stored if there is not one row is written to output.
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size_t count_positive = 0; /// The number of positive rows for the current primary key.
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size_t count_negative = 0; /// The number of negative rows for the current primary key.
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bool last_is_positive = false; /// true if the last row for the current primary key is positive.
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size_t count_incorrect_data = 0; /// To prevent too many error messages from writing to the log.
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size_t blocks_written = 0;
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/// Fields specific for VERTICAL merge algorithm.
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/// Row numbers are relative to the start of current primary key.
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size_t current_pos = 0; /// Current row number
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size_t first_negative_pos = 0; /// Row number of first_negative
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size_t last_positive_pos = 0; /// Row number of last_positive
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size_t last_negative_pos = 0; /// Row number of last_negative
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PODArray<RowSourcePart> current_row_sources; /// Sources of rows with the current primary key
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/** We support two different cursors - with Collation and without.
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* Templates are used instead of polymorphic SortCursors and calls to virtual functions.
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*/
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void merge(MutableColumns & merged_columns, SortingHeap<SortCursor> & queue);
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/// Output to result rows for the current primary key.
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void insertRows(MutableColumns & merged_columns, size_t block_size, MergeStopCondition & condition);
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void reportIncorrectData();
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};
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}
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