ClickHouse/dbms/DataStreams/ReplacingSortedBlockInputStream.h
Ivan 97f2a2213e
Move all folders inside /dbms one level up (#9974)
* Move some code outside dbms/src folder
* Fix paths
2020-04-02 02:51:21 +03:00

62 lines
1.9 KiB
C++

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