ClickHouse/dbms/include/DB/DataStreams/MaterializingBlockInputStream.h

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#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_)
{
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children.push_back(input_);
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}
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String getName() const { return "MaterializingBlockInputStream"; }
String getID() const
{
std::stringstream res;
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res << "Materializing(" << children.back()->getID() << ")";
return res.str();
}
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protected:
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Block readImpl()
{
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Block res = children.back()->read();
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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;
}
};
}