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#include <Functions/IFunction.h>
#include <Functions/FunctionFactory.h>
#include <Functions/FunctionHelpers.h>
#include <DataTypes/DataTypeString.h>
#include <Columns/ColumnString.h>
#include <Interpreters/Context.h>
#include <Common/Macros.h>
#include <Core/Field.h>
namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
extern const int ILLEGAL_COLUMN;
}
namespace
{
/** Get the value of macro from configuration file.
* For example, it may be used as a sophisticated replacement for the function 'hostName' if servers have complicated hostnames
* but you still need to distinguish them by some convenient names.
*/
class FunctionGetMacro : public IFunction
{
private:
MultiVersion<Macros>::Version macros;
bool is_distributed;
public:
static constexpr auto name = "getMacro";
static FunctionPtr create(ContextPtr context)
{
return std::make_shared<FunctionGetMacro>(context->getMacros(), context->isDistributed());
}
explicit FunctionGetMacro(MultiVersion<Macros>::Version macros_, bool is_distributed_)
: macros(std::move(macros_)), is_distributed(is_distributed_)
{
}
String getName() const override
{
return name;
}
bool isDeterministic() const override { return false; }
bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
/// getMacro may return different values on different shards/replicas, so it's not constant for distributed query
bool isSuitableForConstantFolding() const override { return !is_distributed; }
size_t getNumberOfArguments() const override
{
return 1;
}
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
if (!isString(arguments[0]))
throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "The argument of function {} must have String type", getName());
return std::make_shared<DataTypeString>();
}
ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t input_rows_count) const override
{
const IColumn * arg_column = arguments[0].column.get();
const ColumnString * arg_string = checkAndGetColumnConstData<ColumnString>(arg_column);
if (!arg_string)
throw Exception(ErrorCodes::ILLEGAL_COLUMN, "The argument of function {} must be constant String", getName());
return result_type->createColumnConst(input_rows_count, macros->getValue(arg_string->getDataAt(0).toString()));
}
};
}
REGISTER_FUNCTION(GetMacro)
{
factory.registerFunction<FunctionGetMacro>();
}
}
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