ClickHouse/src/Functions/tupleHammingDistance.cpp

#include <Columns/ColumnTuple.h>
#include <Columns/ColumnVector.h>
#include <DataTypes/DataTypeTuple.h>
#include <DataTypes/DataTypesNumber.h>
#include <Functions/FunctionFactory.h>
#include <Functions/FunctionHelpers.h>
#include <Functions/ITupleFunction.h>
#include <Functions/castTypeToEither.h>

namespace DB
{
namespace ErrorCodes
{
    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
}

/// tupleHammingDistance function: (Tuple(...), Tuple(...))-> N
/// Return the number of non-equal tuple elements
class FunctionTupleHammingDistance : public ITupleFunction
{
public:
    static constexpr auto name = "tupleHammingDistance";

    explicit FunctionTupleHammingDistance(ContextPtr context_) : ITupleFunction(context_) {}
    static FunctionPtr create(ContextPtr context_) { return std::make_shared<FunctionTupleHammingDistance>(context_); }

    String getName() const override { return name; }

    size_t getNumberOfArguments() const override { return 2; }

    bool useDefaultImplementationForConstants() const override { return true; }

    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }

    DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
    {
        const auto * left_tuple = checkAndGetDataType<DataTypeTuple>(arguments[0].type.get());
        const auto * right_tuple = checkAndGetDataType<DataTypeTuple>(arguments[1].type.get());

        if (!left_tuple)
            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Argument 0 of function {} should be tuple, got {}",
                            getName(), arguments[0].type->getName());

        if (!right_tuple)
            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Argument 1 of function {} should be tuple, got {}",
                            getName(), arguments[1].type->getName());

        const auto & left_types = left_tuple->getElements();
        const auto & right_types = right_tuple->getElements();

        Columns left_elements;
        Columns right_elements;
        if (arguments[0].column)
            left_elements = getTupleElements(*arguments[0].column);
        if (arguments[1].column)
            right_elements = getTupleElements(*arguments[1].column);

        if (left_types.size() != right_types.size())
            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                            "Expected tuples of the same size as arguments of function {}. Got {} and {}",
                            getName(), arguments[0].type->getName(), arguments[1].type->getName());

        size_t tuple_size = left_types.size();
        if (tuple_size == 0)
            return std::make_shared<DataTypeUInt8>();

        auto compare = FunctionFactory::instance().get("notEquals", context);
        auto plus = FunctionFactory::instance().get("plus", context);
        DataTypePtr res_type;
        for (size_t i = 0; i < tuple_size; ++i)
        {
            try
            {
                ColumnWithTypeAndName left{left_elements.empty() ? nullptr : left_elements[i], left_types[i], {}};
                ColumnWithTypeAndName right{right_elements.empty() ? nullptr : right_elements[i], right_types[i], {}};
                auto elem_compare = compare->build(ColumnsWithTypeAndName{left, right});

                if (i == 0)
                {
                    res_type = elem_compare->getResultType();
                    continue;
                }

                ColumnWithTypeAndName left_type{res_type, {}};
                ColumnWithTypeAndName right_type{elem_compare->getResultType(), {}};
                auto plus_elem = plus->build({left_type, right_type});
                res_type = plus_elem->getResultType();
            }
            catch (DB::Exception & e)
            {
                e.addMessage("While executing function {} for tuple element {}", getName(), i);
                throw;
            }
        }

        return res_type;
    }

    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t input_rows_count) const override
    {
        const auto * left_tuple = checkAndGetDataType<DataTypeTuple>(arguments[0].type.get());
        const auto * right_tuple = checkAndGetDataType<DataTypeTuple>(arguments[1].type.get());
        const auto & left_types = left_tuple->getElements();
        const auto & right_types = right_tuple->getElements();
        auto left_elements = getTupleElements(*arguments[0].column);
        auto right_elements = getTupleElements(*arguments[1].column);

        size_t tuple_size = left_elements.size();
        if (tuple_size == 0)
            return DataTypeUInt8().createColumnConstWithDefaultValue(input_rows_count);

        auto compare = FunctionFactory::instance().get("notEquals", context);
        auto plus = FunctionFactory::instance().get("plus", context);
        ColumnWithTypeAndName res;
        for (size_t i = 0; i < tuple_size; ++i)
        {
            ColumnWithTypeAndName left{left_elements[i], left_types[i], {}};
            ColumnWithTypeAndName right{right_elements[i], right_types[i], {}};
            auto elem_compare = compare->build(ColumnsWithTypeAndName{left, right});

            ColumnWithTypeAndName column;
            column.type = elem_compare->getResultType();
            column.column = elem_compare->execute({left, right}, column.type, input_rows_count);

            if (i == 0)
            {
                res = std::move(column);
            }
            else
            {
                auto plus_elem = plus->build({res, column});
                auto res_type = plus_elem->getResultType();
                res.column = plus_elem->execute({res, column}, res_type, input_rows_count);
                res.type = res_type;
            }
        }

        return res.column;
    }
};

void registerFunctionTupleHammingDistance(FunctionFactory & factory)
{
    factory.registerFunction<FunctionTupleHammingDistance>();
}
}