ClickHouse/dbms/DataStreams/NativeBlockInputStream.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

106 lines
3.0 KiB
C++

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