ClickHouse/dbms/src/Functions/FunctionStringToString.h

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#include <DataTypes/DataTypeString.h>
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#include <Columns/ColumnString.h>
#include <Columns/ColumnFixedString.h>
#include <Functions/FunctionHelpers.h>
#include <Functions/IFunction.h>
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namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_COLUMN;
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
}
template <typename Impl, typename Name, bool is_injective = false>
class FunctionStringToString : public IFunction
{
public:
static constexpr auto name = Name::name;
static FunctionPtr create(const Context &)
{
return std::make_shared<FunctionStringToString>();
}
String getName() const override
{
return name;
}
size_t getNumberOfArguments() const override
{
return 1;
}
bool isInjective(const Block &) override
{
return is_injective;
}
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
if (!isStringOrFixedString(arguments[0]))
throw Exception(
"Illegal type " + arguments[0]->getName() + " of argument of function " + getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
return arguments[0];
}
bool useDefaultImplementationForConstants() const override { return true; }
void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t /*input_rows_count*/) override
{
const ColumnPtr column = block.getByPosition(arguments[0]).column;
if (const ColumnString * col = checkAndGetColumn<ColumnString>(column.get()))
{
auto col_res = ColumnString::create();
Impl::vector(col->getChars(), col->getOffsets(), col_res->getChars(), col_res->getOffsets());
block.getByPosition(result).column = std::move(col_res);
}
else if (const ColumnFixedString * col_fixed = checkAndGetColumn<ColumnFixedString>(column.get()))
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{
auto col_res = ColumnFixedString::create(col_fixed->getN());
Impl::vector_fixed(col_fixed->getChars(), col_fixed->getN(), col_res->getChars());
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block.getByPosition(result).column = std::move(col_res);
}
else
throw Exception(
"Illegal column " + block.getByPosition(arguments[0]).column->getName() + " of argument of function " + getName(),
ErrorCodes::ILLEGAL_COLUMN);
}
};
}