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106 lines
3.0 KiB
C++
106 lines
3.0 KiB
C++
#pragma once
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#include <DataStreams/IBlockInputStream.h>
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#include <DataStreams/MarkInCompressedFile.h>
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#include <Common/PODArray.h>
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namespace DB
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{
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class CompressedReadBufferFromFile;
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/** The Native format can contain a separately located index,
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* which allows you to understand where what column is located,
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* and skip unnecessary columns.
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*/
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/** The position of one piece of a single column. */
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struct IndexOfOneColumnForNativeFormat
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{
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String name;
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String type;
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MarkInCompressedFile location;
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};
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/** The index for the data block. */
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struct IndexOfBlockForNativeFormat
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{
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using Columns = std::vector<IndexOfOneColumnForNativeFormat>;
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size_t num_columns;
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size_t num_rows;
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Columns columns;
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};
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/** The whole index. */
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struct IndexForNativeFormat
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{
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using Blocks = std::vector<IndexOfBlockForNativeFormat>;
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Blocks blocks;
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IndexForNativeFormat() {}
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IndexForNativeFormat(ReadBuffer & istr, const NameSet & required_columns)
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{
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read(istr, required_columns);
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}
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/// Read the index, only for the required columns.
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void read(ReadBuffer & istr, const NameSet & required_columns);
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};
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/** Deserializes the stream of blocks from the native binary format (with names and column types).
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* Designed for communication between servers.
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*
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* Can also be used to store data on disk.
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* In this case, can use the index.
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*/
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class NativeBlockInputStream : public IBlockInputStream
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{
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public:
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/// If a non-zero server_revision is specified, additional block information may be expected and read.
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NativeBlockInputStream(ReadBuffer & istr_, UInt64 server_revision_);
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/// For cases when data structure (header) is known in advance.
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/// NOTE We may use header for data validation and/or type conversions. It is not implemented.
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NativeBlockInputStream(ReadBuffer & istr_, const Block & header_, UInt64 server_revision_);
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/// For cases when we have an index. It allows to skip columns. Only columns specified in the index will be read.
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NativeBlockInputStream(ReadBuffer & istr_, UInt64 server_revision_,
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IndexForNativeFormat::Blocks::const_iterator index_block_it_,
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IndexForNativeFormat::Blocks::const_iterator index_block_end_);
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String getName() const override { return "Native"; }
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static void readData(const IDataType & type, IColumn & column, ReadBuffer & istr, size_t rows, double avg_value_size_hint);
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Block getHeader() const override;
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void resetParser();
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protected:
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Block readImpl() override;
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private:
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ReadBuffer & istr;
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Block header;
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UInt64 server_revision;
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bool use_index = false;
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IndexForNativeFormat::Blocks::const_iterator index_block_it;
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IndexForNativeFormat::Blocks::const_iterator index_block_end;
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IndexOfBlockForNativeFormat::Columns::const_iterator index_column_it;
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/// If an index is specified, then `istr` must be CompressedReadBufferFromFile. Unused otherwise.
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CompressedReadBufferFromFile * istr_concrete = nullptr;
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PODArray<double> avg_value_size_hints;
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void updateAvgValueSizeHints(const Block & block);
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};
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}
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