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72 lines
2.3 KiB
C++
72 lines
2.3 KiB
C++
#pragma once
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#include <Formats/IndexForNativeFormat.h>
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#include <Formats/MarkInCompressedFile.h>
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#include <Common/PODArray.h>
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#include <Core/Block.h>
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namespace DB
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{
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class CompressedReadBufferFromFile;
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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 NativeReader
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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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NativeReader(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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NativeReader(
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ReadBuffer & istr_,
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const Block & header_,
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UInt64 server_revision_,
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bool skip_unknown_columns_ = false,
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bool null_as_default_ = false,
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bool allow_types_conversion_ = false,
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BlockMissingValues * block_missing_values_ = nullptr);
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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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NativeReader(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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static void readData(const ISerialization & serialization, ColumnPtr & column, ReadBuffer & istr, size_t rows, double avg_value_size_hint);
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Block getHeader() const;
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void resetParser();
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Block read();
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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 skip_unknown_columns = false;
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bool null_as_default = false;
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bool allow_types_conversion = false;
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BlockMissingValues * block_missing_values = nullptr;
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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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