ClickHouse/dbms/src/DataStreams/RemoveColumnsBlockInputStream.h
2017-07-17 01:41:15 +03:00

56 lines
1.1 KiB
C++

#pragma once
#include <DataStreams/IProfilingBlockInputStream.h>
namespace DB
{
/** Removes the specified columns from the block.
*/
class RemoveColumnsBlockInputStream : public IProfilingBlockInputStream
{
public:
RemoveColumnsBlockInputStream(
BlockInputStreamPtr input_,
const Names & columns_to_remove_)
: columns_to_remove(columns_to_remove_)
{
children.push_back(input_);
}
String getName() const override { return "RemoveColumns"; }
String getID() const override
{
std::stringstream res;
res << "RemoveColumns(" << children.back()->getID();
for (const auto & it : columns_to_remove)
res << ", " << it;
res << ")";
return res.str();
}
protected:
Block readImpl() override
{
Block res = children.back()->read();
if (!res)
return res;
for (const auto & it : columns_to_remove)
if (res.has(it))
res.erase(it);
return res;
}
private:
Names columns_to_remove;
};
}