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https://github.com/ClickHouse/ClickHouse.git
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97f2a2213e
* Move some code outside dbms/src folder * Fix paths
182 lines
5.3 KiB
C++
182 lines
5.3 KiB
C++
#pragma once
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#include <DataStreams/IBlockInputStream.h>
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#include <IO/ReadBuffer.h>
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#include <Common/PODArray.h>
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namespace Poco { class Logger; }
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namespace DB
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{
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/// Tiny struct, stores number of a Part from which current row was fetched, and insertion flag.
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struct RowSourcePart
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{
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UInt8 data = 0;
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RowSourcePart() = default;
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RowSourcePart(size_t source_num, bool skip_flag = false)
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{
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static_assert(sizeof(*this) == 1, "Size of RowSourcePart is too big due to compiler settings");
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setSourceNum(source_num);
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setSkipFlag(skip_flag);
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}
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size_t getSourceNum() const { return data & MASK_NUMBER; }
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/// In CollapsingMergeTree case flag means "skip this rows"
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bool getSkipFlag() const { return (data & MASK_FLAG) != 0; }
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void setSourceNum(size_t source_num)
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{
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data = (data & MASK_FLAG) | (static_cast<UInt8>(source_num) & MASK_NUMBER);
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}
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void setSkipFlag(bool flag)
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{
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data = flag ? data | MASK_FLAG : data & ~MASK_FLAG;
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}
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static constexpr size_t MAX_PARTS = 0x7F;
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static constexpr UInt8 MASK_NUMBER = 0x7F;
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static constexpr UInt8 MASK_FLAG = 0x80;
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};
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using MergedRowSources = PODArray<RowSourcePart>;
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/** Gather single stream from multiple streams according to streams mask.
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* Stream mask maps row number to index of source stream.
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* Streams should contain exactly one column.
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*/
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class ColumnGathererStream : public IBlockInputStream
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{
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public:
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ColumnGathererStream(
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const String & column_name_, const BlockInputStreams & source_streams, ReadBuffer & row_sources_buf_,
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size_t block_preferred_size_ = DEFAULT_BLOCK_SIZE);
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String getName() const override { return "ColumnGatherer"; }
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Block readImpl() override;
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void readSuffixImpl() override;
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Block getHeader() const override { return children.at(0)->getHeader(); }
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/// for use in implementations of IColumn::gather()
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template <typename Column>
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void gather(Column & column_res);
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private:
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/// Cache required fields
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struct Source
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{
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const IColumn * column = nullptr;
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size_t pos = 0;
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size_t size = 0;
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Block block;
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void update(const String & name)
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{
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column = block.getByName(name).column.get();
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size = block.rows();
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pos = 0;
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}
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};
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void fetchNewBlock(Source & source, size_t source_num);
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String column_name;
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ColumnWithTypeAndName column;
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std::vector<Source> sources;
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ReadBuffer & row_sources_buf;
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size_t block_preferred_size;
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Source * source_to_fully_copy = nullptr;
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Block output_block;
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Poco::Logger * log;
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};
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template <typename Column>
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void ColumnGathererStream::gather(Column & column_res)
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{
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if (source_to_fully_copy) /// Was set on a previous iteration
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{
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output_block.getByPosition(0).column = source_to_fully_copy->block.getByName(column_name).column;
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source_to_fully_copy->pos = source_to_fully_copy->size;
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source_to_fully_copy = nullptr;
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return;
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}
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row_sources_buf.nextIfAtEnd();
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RowSourcePart * row_source_pos = reinterpret_cast<RowSourcePart *>(row_sources_buf.position());
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RowSourcePart * row_sources_end = reinterpret_cast<RowSourcePart *>(row_sources_buf.buffer().end());
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size_t cur_block_preferred_size = std::min(static_cast<size_t>(row_sources_end - row_source_pos), block_preferred_size);
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column_res.reserve(cur_block_preferred_size);
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size_t cur_size = 0;
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while (row_source_pos < row_sources_end && cur_size < cur_block_preferred_size)
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{
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RowSourcePart row_source = *row_source_pos;
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size_t source_num = row_source.getSourceNum();
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Source & source = sources[source_num];
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bool source_skip = row_source.getSkipFlag();
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++row_source_pos;
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if (source.pos >= source.size) /// Fetch new block from source_num part
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{
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fetchNewBlock(source, source_num);
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}
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/// Consecutive optimization. TODO: precompute lengths
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size_t len = 1;
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size_t max_len = std::min(static_cast<size_t>(row_sources_end - row_source_pos), source.size - source.pos); // interval should be in the same block
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while (len < max_len && row_source_pos->data == row_source.data)
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{
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++len;
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++row_source_pos;
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}
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row_sources_buf.position() = reinterpret_cast<char *>(row_source_pos);
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if (!source_skip)
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{
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/// Whole block could be produced via copying pointer from current block
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if (source.pos == 0 && source.size == len)
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{
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/// If current block already contains data, return it.
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/// Whole column from current source will be returned on next read() iteration.
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if (cur_size > 0)
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{
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source_to_fully_copy = &source;
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return;
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}
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output_block.getByPosition(0).column = source.block.getByName(column_name).column;
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source.pos += len;
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return;
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}
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else if (len == 1)
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column_res.insertFrom(*source.column, source.pos);
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else
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column_res.insertRangeFrom(*source.column, source.pos, len);
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cur_size += len;
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}
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source.pos += len;
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}
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}
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}
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