ClickHouse/dbms/src/Functions/hostName.cpp
2018-09-09 01:04:39 +03:00

59 lines
1.5 KiB
C++

#include <Functions/IFunction.h>
#include <Functions/FunctionFactory.h>
#include <DataTypes/DataTypeString.h>
#include <Common/DNSResolver.h>
namespace DB
{
/// Get the host name. Is is constant on single server, but is not constant in distributed queries.
class FunctionHostName : public IFunction
{
public:
static constexpr auto name = "hostName";
static FunctionPtr create(const Context &)
{
return std::make_shared<FunctionHostName>();
}
String getName() const override
{
return name;
}
bool isDeterministic() const override { return false; }
bool isDeterministicInScopeOfQuery() const override
{
return false;
}
size_t getNumberOfArguments() const override
{
return 0;
}
DataTypePtr getReturnTypeImpl(const DataTypes & /*arguments*/) const override
{
return std::make_shared<DataTypeString>();
}
/** convertToFullColumn needed because in distributed query processing,
* each server returns its own value.
*/
void executeImpl(Block & block, const ColumnNumbers &, size_t result, size_t input_rows_count) override
{
block.getByPosition(result).column = block.getByPosition(result).type->createColumnConst(
input_rows_count, DNSResolver::instance().getHostName())->convertToFullColumnIfConst();
}
};
void registerFunctionHostName(FunctionFactory & factory)
{
factory.registerFunction<FunctionHostName>();
}
}