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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}
String getName() const override { return "Materializing"; }
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String getID() const override
{
std::stringstream res;
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res << "Materializing(" << children.back()->getID() << ")";
return res.str();
}
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protected:
Block readImpl() override
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{
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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)
{
auto & src = res.getByPosition(i).column;
ColumnPtr converted = src->convertToFullColumnIfConst();
if (converted)
src = converted;
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}
return res;
}
};
}