ClickHouse/dbms/include/DB/DataStreams/MaterializingBlockInputStream.h
2011-11-06 06:22:52 +00:00

49 lines
1000 B
C++

#pragma once
#include <DB/Columns/ColumnConst.h>
#include <DB/DataStreams/IProfilingBlockInputStream.h>
namespace DB
{
/** Преобразует столбцы-константы в полноценные столбцы ("материализует" их).
*/
class MaterializingBlockInputStream : public IProfilingBlockInputStream
{
public:
MaterializingBlockInputStream(BlockInputStreamPtr input_)
: input(input_)
{
children.push_back(input);
}
Block readImpl()
{
Block res = input->read();
if (!res)
return res;
size_t columns = res.columns();
for (size_t i = 0; i < columns; ++i)
{
ColumnPtr col = res.getByPosition(i).column;
if (col->isConst())
res.getByPosition(i).column = dynamic_cast<IColumnConst &>(*col).convertToFullColumn();
}
return res;
}
String getName() const { return "MaterializingBlockInputStream"; }
BlockInputStreamPtr clone() { return new MaterializingBlockInputStream(input); }
private:
BlockInputStreamPtr input;
};
}