#pragma once

#include <DB/Columns/ColumnsNumber.h>
#include <DB/Columns/ColumnConst.h>
#include <DB/Columns/ColumnString.h>
#include <DB/Columns/ColumnFixedString.h>
#include <DB/Columns/ColumnTuple.h>

#include <DB/DataTypes/DataTypesNumberFixed.h>
#include <DB/DataTypes/DataTypeDateTime.h>
#include <DB/DataTypes/DataTypeDate.h>
#include <DB/DataTypes/DataTypeString.h>
#include <DB/DataTypes/DataTypeFixedString.h>
#include <DB/DataTypes/DataTypeTuple.h>

#include <DB/Functions/FunctionsLogical.h>
#include <DB/Functions/IFunction.h>
#include <DB/DataTypes/DataTypeEnum.h>


namespace DB
{

/** Функции сравнения: ==, !=, <, >, <=, >=.
  * Функции сравнения возвращают всегда 0 или 1 (UInt8).
  *
  * Сравнивать можно следующие типы:
  * - числа;
  * - строки и фиксированные строки;
  * - даты;
  * - даты-с-временем;
  *   внутри каждой группы, но не из разных групп;
  * - кортежи (сравнение лексикографическое).
  *
  * Исключение: можно сравнивать дату и дату-с-временем с константной строкой. Пример: EventDate = '2015-01-01'.
  *
  * TODO Массивы.
  */

/** Игнорируем warning о сравнении signed и unsigned.
  * (Результат может быть некорректным.)
  */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-compare"

template <typename A, typename B> struct EqualsOp 			{ static UInt8 apply(A a, B b) { return a == b; } };
template <typename A, typename B> struct NotEqualsOp 		{ static UInt8 apply(A a, B b) { return a != b; } };
template <typename A, typename B> struct LessOp 			{ static UInt8 apply(A a, B b) { return a < b; 	} };
template <typename A, typename B> struct GreaterOp 			{ static UInt8 apply(A a, B b) { return a > b; 	} };
template <typename A, typename B> struct LessOrEqualsOp 	{ static UInt8 apply(A a, B b) { return a <= b; } };
template <typename A, typename B> struct GreaterOrEqualsOp 	{ static UInt8 apply(A a, B b) { return a >= b; } };

#pragma GCC diagnostic pop



template<typename A, typename B, typename Op>
struct NumComparisonImpl
{
	static void vector_vector(const PaddedPODArray<A> & a, const PaddedPODArray<B> & b, PaddedPODArray<UInt8> & c)
	{
		/** GCC 4.8.2 векторизует цикл только если его записать в такой форме.
		  * В данном случае, если сделать цикл по индексу массива (код будет выглядеть проще),
		  *  цикл не будет векторизовываться.
		  */

		size_t size = a.size();
		const A * a_pos = &a[0];
		const B * b_pos = &b[0];
		UInt8 * c_pos = &c[0];
		const A * a_end = a_pos + size;

		while (a_pos < a_end)
		{
			*c_pos = Op::apply(*a_pos, *b_pos);
			++a_pos;
			++b_pos;
			++c_pos;
		}
	}

	static void vector_constant(const PaddedPODArray<A> & a, B b, PaddedPODArray<UInt8> & c)
	{
		size_t size = a.size();
		const A * a_pos = &a[0];
		UInt8 * c_pos = &c[0];
		const A * a_end = a_pos + size;

		while (a_pos < a_end)
		{
			*c_pos = Op::apply(*a_pos, b);
			++a_pos;
			++c_pos;
		}
	}

	static void constant_vector(A a, const PaddedPODArray<B> & b, PaddedPODArray<UInt8> & c)
	{
		size_t size = b.size();
		const B * b_pos = &b[0];
		UInt8 * c_pos = &c[0];
		const B * b_end = b_pos + size;

		while (b_pos < b_end)
		{
			*c_pos = Op::apply(a, *b_pos);
			++b_pos;
			++c_pos;
		}
	}

	static void constant_constant(A a, B b, UInt8 & c)
	{
		c = Op::apply(a, b);
	}
};


template <typename Op>
struct StringComparisonImpl
{
	static void string_vector_string_vector(
		const ColumnString::Chars_t & a_data, const ColumnString::Offsets_t & a_offsets,
		const ColumnString::Chars_t & b_data, const ColumnString::Offsets_t & b_offsets,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_offsets.size();
		for (size_t i = 0; i < size; ++i)
		{
			if (i == 0)
			{
				/// Завершающий ноль в меньшей по длине строке входит в сравнение.
				c[i] = Op::apply(memcmp(&a_data[0], &b_data[0], std::min(a_offsets[0], b_offsets[0])), 0);
			}
			else
			{
				c[i] = Op::apply(memcmp(&a_data[a_offsets[i - 1]], &b_data[b_offsets[i - 1]],
					std::min(a_offsets[i] - a_offsets[i - 1], b_offsets[i] - b_offsets[i - 1])), 0);
			}
		}
	}

	static void string_vector_fixed_string_vector(
		const ColumnString::Chars_t & a_data, const ColumnString::Offsets_t & a_offsets,
		const ColumnString::Chars_t & b_data, ColumnString::Offset_t b_n,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_offsets.size();
		for (size_t i = 0; i < size; ++i)
		{
			if (i == 0)
			{
				int res = memcmp(&a_data[0], &b_data[0], std::min(a_offsets[0] - 1, b_n));
				c[i] = Op::apply(res, 0) || (res == 0 && Op::apply(a_offsets[0], b_n + 1));
			}
			else
			{
				int res = memcmp(&a_data[a_offsets[i - 1]], &b_data[i * b_n],
					std::min(a_offsets[i] - a_offsets[i - 1] - 1, b_n));
				c[i] = Op::apply(res, 0) || (res == 0 && Op::apply(a_offsets[i] - a_offsets[i - 1], b_n + 1));
			}
		}
	}

	static void string_vector_constant(
		const ColumnString::Chars_t & a_data, const ColumnString::Offsets_t & a_offsets,
		const std::string & b,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_offsets.size();
		ColumnString::Offset_t b_n = b.size();
		const UInt8 * b_data = reinterpret_cast<const UInt8 *>(b.data());
		for (size_t i = 0; i < size; ++i)
		{
			if (i == 0)
			{
				c[i] = Op::apply(memcmp(&a_data[0], b_data, std::min(a_offsets[0], b_n + 1)), 0);
			}
			else
			{
				c[i] = Op::apply(memcmp(&a_data[a_offsets[i - 1]], b_data,
					std::min(a_offsets[i] - a_offsets[i - 1], b_n + 1)), 0);
			}
		}
	}

	static void fixed_string_vector_string_vector(
		const ColumnString::Chars_t & a_data, ColumnString::Offset_t a_n,
		const ColumnString::Chars_t & b_data, const ColumnString::Offsets_t & b_offsets,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = b_offsets.size();
		for (size_t i = 0; i < size; ++i)
		{
			if (i == 0)
			{
				int res = memcmp(&a_data[0], &b_data[0], std::min(b_offsets[0] - 1, a_n));
				c[i] = Op::apply(res, 0) || (res == 0 && Op::apply(a_n + 1, b_offsets[0]));
			}
			else
			{
				int res = memcmp(&a_data[i * a_n], &b_data[b_offsets[i - 1]],
					std::min(b_offsets[i] - b_offsets[i - 1] - 1, a_n));
				c[i] = Op::apply(res, 0) || (res == 0 && Op::apply(a_n + 1, b_offsets[i] - b_offsets[i - 1]));
			}
		}
	}

	static void fixed_string_vector_fixed_string_vector(
		const ColumnString::Chars_t & a_data, ColumnString::Offset_t a_n,
		const ColumnString::Chars_t & b_data, ColumnString::Offset_t b_n,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_data.size();
		for (size_t i = 0, j = 0; i < size; i += a_n, ++j)
		{
			int res = memcmp(&a_data[i], &b_data[i], std::min(a_n, b_n));
			c[j] = Op::apply(res, 0) || (res == 0 && Op::apply(a_n, b_n));
		}
	}

	static void fixed_string_vector_constant(
		const ColumnString::Chars_t & a_data, ColumnString::Offset_t a_n,
		const std::string & b,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_data.size();
		const UInt8 * b_data = reinterpret_cast<const UInt8 *>(b.data());
		ColumnString::Offset_t b_n = b.size();
		for (size_t i = 0, j = 0; i < size; i += a_n, ++j)
		{
			int res = memcmp(&a_data[i], b_data, std::min(a_n, b_n));
			c[j] = Op::apply(res, 0) || (res == 0 && Op::apply(a_n, b_n));
		}
	}

	static void constant_string_vector(
		const std::string & a,
		const ColumnString::Chars_t & b_data, const ColumnString::Offsets_t & b_offsets,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = b_offsets.size();
		ColumnString::Offset_t a_n = a.size();
		const UInt8 * a_data = reinterpret_cast<const UInt8 *>(a.data());
		for (size_t i = 0; i < size; ++i)
		{
			if (i == 0)
			{
				c[i] = Op::apply(memcmp(a_data, &b_data[0], std::min(b_offsets[0], a_n + 1)), 0);
			}
			else
			{
				c[i] = Op::apply(memcmp(a_data, &b_data[b_offsets[i - 1]],
					std::min(b_offsets[i] - b_offsets[i - 1], a_n + 1)), 0);
			}
		}
	}

	static void constant_fixed_string_vector(
		const std::string & a,
		const ColumnString::Chars_t & b_data, ColumnString::Offset_t b_n,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = b_data.size();
		const UInt8 * a_data = reinterpret_cast<const UInt8 *>(a.data());
		ColumnString::Offset_t a_n = a.size();
		for (size_t i = 0, j = 0; i < size; i += b_n, ++j)
		{
			int res = memcmp(a_data, &b_data[i], std::min(a_n, b_n));
			c[j] = Op::apply(res, 0) || (res == 0 && Op::apply(b_n, a_n));
		}
	}

	static void constant_constant(
		const std::string & a,
		const std::string & b,
		UInt8 & c)
	{
		c = Op::apply(memcmp(a.data(), b.data(), std::min(a.size(), b.size()) + 1), 0);
	}
};


/// Сравнения на равенство/неравенство реализованы несколько более эффективно.
template <bool positive>
struct StringEqualsImpl
{
	static void string_vector_string_vector(
		const ColumnString::Chars_t & a_data, const ColumnString::Offsets_t & a_offsets,
		const ColumnString::Chars_t & b_data, const ColumnString::Offsets_t & b_offsets,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_offsets.size();
		for (size_t i = 0; i < size; ++i)
			c[i] = positive == ((i == 0)
				? (a_offsets[0] == b_offsets[0] && !memcmp(&a_data[0], &b_data[0], a_offsets[0] - 1))
				: (a_offsets[i] - a_offsets[i - 1] == b_offsets[i] - b_offsets[i - 1]
					&& !memcmp(&a_data[a_offsets[i - 1]], &b_data[b_offsets[i - 1]], a_offsets[i] - a_offsets[i - 1] - 1)));
	}

	static void string_vector_fixed_string_vector(
		const ColumnString::Chars_t & a_data, const ColumnString::Offsets_t & a_offsets,
		const ColumnString::Chars_t & b_data, ColumnString::Offset_t b_n,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_offsets.size();
		for (size_t i = 0; i < size; ++i)
			c[i] = positive == ((i == 0)
				? (a_offsets[0] == b_n + 1 && !memcmp(&a_data[0], &b_data[0], b_n))
				: (a_offsets[i] - a_offsets[i - 1] == b_n + 1
					&& !memcmp(&a_data[a_offsets[i - 1]], &b_data[b_n * i], b_n)));
	}

	static void string_vector_constant(
		const ColumnString::Chars_t & a_data, const ColumnString::Offsets_t & a_offsets,
		const std::string & b,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_offsets.size();
		ColumnString::Offset_t b_n = b.size();
		const UInt8 * b_data = reinterpret_cast<const UInt8 *>(b.data());
		for (size_t i = 0; i < size; ++i)
			c[i] = positive == ((i == 0)
				? (a_offsets[0] == b_n + 1 && !memcmp(&a_data[0], b_data, b_n))
				: (a_offsets[i] - a_offsets[i - 1] == b_n + 1
					&& !memcmp(&a_data[a_offsets[i - 1]], b_data, b_n)));
	}

	static void fixed_string_vector_fixed_string_vector(
		const ColumnString::Chars_t & a_data, ColumnString::Offset_t a_n,
		const ColumnString::Chars_t & b_data, ColumnString::Offset_t b_n,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_data.size();
		for (size_t i = 0, j = 0; i < size; i += a_n, ++j)
			c[j] = positive == (a_n == b_n && !memcmp(&a_data[i], &b_data[i], a_n));
	}

	static void fixed_string_vector_constant(
		const ColumnString::Chars_t & a_data, ColumnString::Offset_t a_n,
		const std::string & b,
		PaddedPODArray<UInt8> & c)
	{
		size_t size = a_data.size();
		const UInt8 * b_data = reinterpret_cast<const UInt8 *>(b.data());
		ColumnString::Offset_t b_n = b.size();
		for (size_t i = 0, j = 0; i < size; i += a_n, ++j)
			c[j] = positive == (a_n == b_n && !memcmp(&a_data[i], b_data, a_n));
	}

	static void constant_constant(
		const std::string & a,
		const std::string & b,
		UInt8 & c)
	{
		c = positive == (a == b);
	}

	static void fixed_string_vector_string_vector(
		const ColumnString::Chars_t & a_data, ColumnString::Offset_t a_n,
		const ColumnString::Chars_t & b_data, const ColumnString::Offsets_t & b_offsets,
		PaddedPODArray<UInt8> & c)
	{
		string_vector_fixed_string_vector(b_data, b_offsets, a_data, a_n, c);
	}

	static void constant_string_vector(
		const std::string & a,
		const ColumnString::Chars_t & b_data, const ColumnString::Offsets_t & b_offsets,
		PaddedPODArray<UInt8> & c)
	{
		string_vector_constant(b_data, b_offsets, a, c);
	}

	static void constant_fixed_string_vector(
		const std::string & a,
		const ColumnString::Chars_t & b_data, ColumnString::Offset_t b_n,
		PaddedPODArray<UInt8> & c)
	{
		fixed_string_vector_constant(b_data, b_n, a, c);
	}
};


template <typename A, typename B>
struct StringComparisonImpl<EqualsOp<A, B>> : StringEqualsImpl<true> {};

template <typename A, typename B>
struct StringComparisonImpl<NotEqualsOp<A, B>> : StringEqualsImpl<false> {};


struct NameEquals 			{ static constexpr auto name = "equals"; };
struct NameNotEquals 		{ static constexpr auto name = "notEquals"; };
struct NameLess 			{ static constexpr auto name = "less"; };
struct NameGreater 			{ static constexpr auto name = "greater"; };
struct NameLessOrEquals 	{ static constexpr auto name = "lessOrEquals"; };
struct NameGreaterOrEquals 	{ static constexpr auto name = "greaterOrEquals"; };


template <
	template <typename, typename> class Op,
	typename Name>
class FunctionComparison : public IFunction
{
public:
	static constexpr auto name = Name::name;
	static FunctionPtr create(const Context & context) { return std::make_shared<FunctionComparison>(); };

private:
	template <typename T0, typename T1>
	bool executeNumRightType(Block & block, size_t result, const ColumnVector<T0> * col_left, const IColumn * col_right_untyped)
	{
		if (const ColumnVector<T1> * col_right = typeid_cast<const ColumnVector<T1> *>(col_right_untyped))
		{
			std::shared_ptr<ColumnUInt8> col_res = std::make_shared<ColumnUInt8>();
			block.getByPosition(result).column = col_res;

			ColumnUInt8::Container_t & vec_res = col_res->getData();
			vec_res.resize(col_left->getData().size());
			NumComparisonImpl<T0, T1, Op<T0, T1>>::vector_vector(col_left->getData(), col_right->getData(), vec_res);

			return true;
		}
		else if (const ColumnConst<T1> * col_right = typeid_cast<const ColumnConst<T1> *>(col_right_untyped))
		{
			std::shared_ptr<ColumnUInt8> col_res = std::make_shared<ColumnUInt8>();
			block.getByPosition(result).column = col_res;

			ColumnUInt8::Container_t & vec_res = col_res->getData();
			vec_res.resize(col_left->getData().size());
			NumComparisonImpl<T0, T1, Op<T0, T1>>::vector_constant(col_left->getData(), col_right->getData(), vec_res);

			return true;
		}

		return false;
	}

	template <typename T0, typename T1>
	bool executeNumConstRightType(Block & block, size_t result, const ColumnConst<T0> * col_left, const IColumn * col_right_untyped)
	{
		if (const ColumnVector<T1> * col_right = typeid_cast<const ColumnVector<T1> *>(col_right_untyped))
		{
			std::shared_ptr<ColumnUInt8> col_res = std::make_shared<ColumnUInt8>();
			block.getByPosition(result).column = col_res;

			ColumnUInt8::Container_t & vec_res = col_res->getData();
			vec_res.resize(col_left->size());
			NumComparisonImpl<T0, T1, Op<T0, T1>>::constant_vector(col_left->getData(), col_right->getData(), vec_res);

			return true;
		}
		else if (const ColumnConst<T1> * col_right = typeid_cast<const ColumnConst<T1> *>(col_right_untyped))
		{
			UInt8 res = 0;
			NumComparisonImpl<T0, T1, Op<T0, T1>>::constant_constant(col_left->getData(), col_right->getData(), res);

			auto col_res = std::make_shared<ColumnConstUInt8>(col_left->size(), res);
			block.getByPosition(result).column = col_res;

			return true;
		}

		return false;
	}

	template <typename T0>
	bool executeNumLeftType(Block & block, size_t result, const IColumn * col_left_untyped, const IColumn * col_right_untyped)
	{
		if (const ColumnVector<T0> * col_left = typeid_cast<const ColumnVector<T0> *>(col_left_untyped))
		{
			if (	executeNumRightType<T0, UInt8>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, UInt16>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, UInt32>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, UInt64>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, Int8>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, Int16>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, Int32>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, Int64>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, Float32>(block, result, col_left, col_right_untyped)
				||	executeNumRightType<T0, Float64>(block, result, col_left, col_right_untyped))
				return true;
			else
				throw Exception("Illegal column " + col_right_untyped->getName()
					+ " of second argument of function " + getName(),
					ErrorCodes::ILLEGAL_COLUMN);
		}
		else if (const ColumnConst<T0> * col_left = typeid_cast<const ColumnConst<T0> *>(col_left_untyped))
		{
			if (	executeNumConstRightType<T0, UInt8>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, UInt16>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, UInt32>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, UInt64>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, Int8>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, Int16>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, Int32>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, Int64>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, Float32>(block, result, col_left, col_right_untyped)
				||	executeNumConstRightType<T0, Float64>(block, result, col_left, col_right_untyped))
				return true;
			else
				throw Exception("Illegal column " + col_right_untyped->getName()
					+ " of second argument of function " + getName(),
					ErrorCodes::ILLEGAL_COLUMN);
		}

		return false;
	}

	void executeString(Block & block, size_t result, const IColumn * c0, const IColumn * c1)
	{
		const ColumnString * c0_string = typeid_cast<const ColumnString *>(c0);
		const ColumnString * c1_string = typeid_cast<const ColumnString *>(c1);
		const ColumnFixedString * c0_fixed_string = typeid_cast<const ColumnFixedString *>(c0);
		const ColumnFixedString * c1_fixed_string = typeid_cast<const ColumnFixedString *>(c1);
		const ColumnConstString * c0_const = typeid_cast<const ColumnConstString *>(c0);
		const ColumnConstString * c1_const = typeid_cast<const ColumnConstString *>(c1);

		using StringImpl = StringComparisonImpl<Op<int, int>>;

		if (c0_const && c1_const)
		{
			auto c_res = std::make_shared<ColumnConstUInt8>(c0_const->size(), 0);
			block.getByPosition(result).column = c_res;
			StringImpl::constant_constant(c0_const->getData(), c1_const->getData(), c_res->getData());
		}
		else
		{
			auto c_res = std::make_shared<ColumnUInt8>();
			block.getByPosition(result).column = c_res;
			ColumnUInt8::Container_t & vec_res = c_res->getData();
			vec_res.resize(c0->size());

			if (c0_string && c1_string)
				StringImpl::string_vector_string_vector(
					c0_string->getChars(), c0_string->getOffsets(),
					c1_string->getChars(), c1_string->getOffsets(),
					c_res->getData());
			else if (c0_string && c1_fixed_string)
				StringImpl::string_vector_fixed_string_vector(
					c0_string->getChars(), c0_string->getOffsets(),
					c1_fixed_string->getChars(), c1_fixed_string->getN(),
					c_res->getData());
			else if (c0_string && c1_const)
				StringImpl::string_vector_constant(
					c0_string->getChars(), c0_string->getOffsets(),
					c1_const->getData(),
					c_res->getData());
			else if (c0_fixed_string && c1_string)
				StringImpl::fixed_string_vector_string_vector(
					c0_fixed_string->getChars(), c0_fixed_string->getN(),
					c1_string->getChars(), c1_string->getOffsets(),
					c_res->getData());
			else if (c0_fixed_string && c1_fixed_string)
				StringImpl::fixed_string_vector_fixed_string_vector(
					c0_fixed_string->getChars(), c0_fixed_string->getN(),
					c1_fixed_string->getChars(), c1_fixed_string->getN(),
					c_res->getData());
			else if (c0_fixed_string && c1_const)
				StringImpl::fixed_string_vector_constant(
					c0_fixed_string->getChars(), c0_fixed_string->getN(),
					c1_const->getData(),
					c_res->getData());
			else if (c0_const && c1_string)
				StringImpl::constant_string_vector(
					c0_const->getData(),
					c1_string->getChars(), c1_string->getOffsets(),
					c_res->getData());
			else if (c0_const && c1_fixed_string)
				StringImpl::constant_fixed_string_vector(
					c0_const->getData(),
					c1_fixed_string->getChars(), c1_fixed_string->getN(),
					c_res->getData());
			else
				throw Exception("Illegal columns "
					+ c0->getName() + " and " + c1->getName()
					+ " of arguments of function " + getName(),
					ErrorCodes::ILLEGAL_COLUMN);
		}
	}

	void executeDateOrDateTimeOrEnumWithConstString(
		Block & block, size_t result, const IColumn * col_left_untyped, const IColumn * col_right_untyped,
		const DataTypePtr & left_type, const DataTypePtr & right_type, bool left_is_num, bool right_is_num)
	{
		/// Уже не такой и особый случай - сравнение дат, дат-с-временем и перечислений со строковой константой.
		const IColumn * column_string_untyped = !left_is_num ? col_left_untyped : col_right_untyped;
		const IColumn * column_number = left_is_num ? col_left_untyped : col_right_untyped;
		const IDataType * number_type = left_is_num ? left_type.get() : right_type.get();

		bool is_date = false;
		bool is_date_time = false;
		bool is_enum8 = false;
		bool is_enum16 = false;

		const auto legal_types = (is_date = typeid_cast<const DataTypeDate *>(number_type))
			|| (is_date_time = typeid_cast<const DataTypeDateTime *>(number_type))
			|| (is_enum8 = typeid_cast<const DataTypeEnum8 *>(number_type))
			|| (is_enum16 = typeid_cast<const DataTypeEnum16 *>(number_type));

		const auto column_string = typeid_cast<const ColumnConstString *>(column_string_untyped);
		if (!column_string || !legal_types)
			throw Exception{
				"Illegal columns " + col_left_untyped->getName() + " and " + col_right_untyped->getName()
					+ " of arguments of function " + getName(),
				ErrorCodes::ILLEGAL_COLUMN
			};

		if (is_date)
		{
			DayNum_t date;
			ReadBufferFromString in(column_string->getData());
			readDateText(date, in);
			if (!in.eof())
				throw Exception("String is too long for Date: " + column_string->getData());

			ColumnConst<DataTypeDate::FieldType> parsed_const_date(block.rowsInFirstColumn(), date);
			executeNumLeftType<DataTypeDate::FieldType>(block, result,
				left_is_num ? col_left_untyped : &parsed_const_date,
				left_is_num ? &parsed_const_date : col_right_untyped);
		}
		else if (is_date_time)
		{
			time_t date_time;
			ReadBufferFromString in(column_string->getData());
			readDateTimeText(date_time, in);
			if (!in.eof())
				throw Exception("String is too long for DateTime: " + column_string->getData());

			ColumnConst<DataTypeDateTime::FieldType> parsed_const_date_time(block.rowsInFirstColumn(), date_time);
			executeNumLeftType<DataTypeDateTime::FieldType>(block, result,
				left_is_num ? col_left_untyped : &parsed_const_date_time,
				left_is_num ? &parsed_const_date_time : col_right_untyped);
		}
		else if (is_enum8)
			executeEnumWithConstString<DataTypeEnum8>(block, result, column_number, column_string,
				number_type, left_is_num);
		else if (is_enum16)
			executeEnumWithConstString<DataTypeEnum16>(block, result, column_number, column_string,
				number_type, left_is_num);
	}

	/// Comparison between DataTypeEnum<T> and string constant containing the name of an enum element
	template <typename EnumType>
	void executeEnumWithConstString(
		Block & block, const size_t result, const IColumn * column_number, const ColumnConstString * column_string,
		const IDataType * type_untyped, const bool left_is_num)
	{
		const auto type = static_cast<const EnumType *>(type_untyped);

		const Field x = nearestFieldType(type->getValue(column_string->getData()));
		const auto enum_col = type->createConstColumn(block.rowsInFirstColumn(), x);

		executeNumLeftType<typename EnumType::FieldType>(block, result,
			left_is_num ? column_number : enum_col.get(),
			left_is_num ? enum_col.get() : column_number);
	}

	void executeTuple(Block & block, size_t result, const IColumn * c0, const IColumn * c1)
	{
		/** Сравнивать кортежи будем лексикографически. Это делается следующим образом:
		  * x == y : x1 == y1 && x2 == y2 ...
		  * x != y : x1 != y1 || x2 != y2 ...
		  *
		  * x < y:   x1 < y1 || (x1 == y1 && (x2 < y2 || (x2 == y2 ... && xn < yn))
		  * x > y:   x1 > y1 || (x1 == y1 && (x2 > y2 || (x2 == y2 ... && xn > yn))
		  * x <= y:  x1 < y1 || (x1 == y1 && (x2 < y2 || (x2 == y2 ... && xn <= yn))
		  *
 		  * Рекурсивная запись:
		  * x <= y:  x1 < y1 || (x1 == y1 && x_tail <= y_tail)
		  *
		  * x >= y:  x1 > y1 || (x1 == y1 && (x2 > y2 || (x2 == y2 ... && xn >= yn))
		  */

		auto x_const = typeid_cast<const ColumnConstTuple *>(c0);
		auto y_const = typeid_cast<const ColumnConstTuple *>(c1);

		ColumnPtr x_tuple_of_consts;
		ColumnPtr y_tuple_of_consts;

		auto x = static_cast<const ColumnTuple *>(c0);
		auto y = static_cast<const ColumnTuple *>(c1);

		if (x_const)
		{
			x_tuple_of_consts = x_const->convertToTupleOfConstants();
			x = static_cast<const ColumnTuple *>(x_tuple_of_consts.get());
		}

		if (y_const)
		{
			y_tuple_of_consts = y_const->convertToTupleOfConstants();
			y = static_cast<const ColumnTuple *>(y_tuple_of_consts.get());
		}

		const size_t tuple_size = x->getData().columns();

		if (0 == tuple_size)
			throw Exception("Comparison of zero-sized tuples is not implemented.", ErrorCodes::NOT_IMPLEMENTED);

		executeTupleImpl(block, result, x, y, tuple_size);
	}

	void executeTupleImpl(Block & block, size_t result, const ColumnTuple * x, const ColumnTuple * y, size_t tuple_size);

	template <typename ComparisonFunction, typename ConvolutionFunction>
	void executeTupleEqualityImpl(Block & block, size_t result, const ColumnTuple * x, const ColumnTuple * y, size_t tuple_size)
	{
		ComparisonFunction func_compare;
		ConvolutionFunction func_convolution;

		Block tmp_block;
		for (size_t i = 0; i < tuple_size; ++i)
		{
			tmp_block.insert(x->getData().getByPosition(i));
			tmp_block.insert(y->getData().getByPosition(i));

			/// Сравнение элементов.
			tmp_block.insert({ nullptr, std::make_shared<DataTypeUInt8>(), "" });
			func_compare.execute(tmp_block, {i * 3, i * 3 + 1}, i * 3 + 2);
		}

		/// Логическая свёртка.
		tmp_block.insert({ nullptr, std::make_shared<DataTypeUInt8>(), "" });

		ColumnNumbers convolution_args(tuple_size);
		for (size_t i = 0; i < tuple_size; ++i)
			convolution_args[i] = i * 3 + 2;

		func_convolution.execute(tmp_block, convolution_args, tuple_size * 3);
		block.getByPosition(result).column = tmp_block.getByPosition(tuple_size * 3).column;
	}

	template <typename HeadComparisonFunction, typename TailComparisonFunction>
	void executeTupleLessGreaterImpl(Block & block, size_t result, const ColumnTuple * x, const ColumnTuple * y, size_t tuple_size)
	{
		HeadComparisonFunction func_compare_head;
		TailComparisonFunction func_compare_tail;
		FunctionAnd func_and;
		FunctionOr func_or;
		FunctionComparison<EqualsOp, NameEquals> func_equals;

		Block tmp_block;

		/// Попарное сравнение на неравенство всех элементов; на равенство всех элементов кроме последнего.
		for (size_t i = 0; i < tuple_size; ++i)
		{
			tmp_block.insert(x->getData().getByPosition(i));
			tmp_block.insert(y->getData().getByPosition(i));

			tmp_block.insert({ nullptr, std::make_shared<DataTypeUInt8>(), "" });

			if (i + 1 != tuple_size)
			{
				func_compare_head.execute(tmp_block, {i * 4, i * 4 + 1}, i * 4 + 2);

				tmp_block.insert({ nullptr, std::make_shared<DataTypeUInt8>(), "" });
				func_equals.execute(tmp_block, {i * 4, i * 4 + 1}, i * 4 + 3);

			}
			else
				func_compare_tail.execute(tmp_block, {i * 4, i * 4 + 1}, i * 4 + 2);
		}

		/// Комбинирование. Сложный код - сделайте рисунок. Можно заменить на рекурсивное сравнение кортежей.
		size_t i = tuple_size - 1;
		while (i > 0)
		{
			tmp_block.insert({ nullptr, std::make_shared<DataTypeUInt8>(), "" });
			func_and.execute(tmp_block, { tmp_block.columns() - 2, (i - 1) * 4 + 3 },  tmp_block.columns() - 1);
			tmp_block.insert({ nullptr, std::make_shared<DataTypeUInt8>(), "" });
			func_or.execute(tmp_block, { tmp_block.columns() - 2, (i - 1) * 4 + 2 },  tmp_block.columns() - 1);
			--i;
		}

		block.getByPosition(result).column = tmp_block.getByPosition(tmp_block.columns() - 1).column;
	}


public:
	/// Получить имя функции.
	String getName() const override
	{
		return name;
	}

	size_t getNumberOfArguments() const override { return 2; }

	/// Получить типы результата по типам аргументов. Если функция неприменима для данных аргументов - кинуть исключение.
	DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
	{
		bool left_is_date = false;
		bool left_is_date_time = false;
		bool left_is_enum8 = false;
		bool left_is_enum16 = false;
		bool left_is_string = false;
		bool left_is_fixed_string = false;
		const DataTypeTuple * left_tuple = nullptr;

		false
			|| (left_is_date 		= typeid_cast<const DataTypeDate *>(arguments[0].get()))
			|| (left_is_date_time 	= typeid_cast<const DataTypeDateTime *>(arguments[0].get()))
			|| (left_is_enum8 		= typeid_cast<const DataTypeEnum8 *>(arguments[0].get()))
			|| (left_is_enum16 		= typeid_cast<const DataTypeEnum16 *>(arguments[0].get()))
			|| (left_is_string 		= typeid_cast<const DataTypeString *>(arguments[0].get()))
			|| (left_is_fixed_string = typeid_cast<const DataTypeFixedString *>(arguments[0].get()))
			|| (left_tuple 			= typeid_cast<const DataTypeTuple *>(arguments[0].get()));

		const bool left_is_enum = left_is_enum8 || left_is_enum16;

		bool right_is_date = false;
		bool right_is_date_time = false;
		bool right_is_enum8 = false;
		bool right_is_enum16 = false;
		bool right_is_string = false;
		bool right_is_fixed_string = false;
		const DataTypeTuple * right_tuple = nullptr;

		false
			|| (right_is_date 		= typeid_cast<const DataTypeDate *>(arguments[1].get()))
			|| (right_is_date_time 	= typeid_cast<const DataTypeDateTime *>(arguments[1].get()))
			|| (right_is_enum8 		= typeid_cast<const DataTypeEnum8 *>(arguments[1].get()))
			|| (right_is_enum16 	= typeid_cast<const DataTypeEnum16 *>(arguments[1].get()))
			|| (right_is_string 	= typeid_cast<const DataTypeString *>(arguments[1].get()))
			|| (right_is_fixed_string = typeid_cast<const DataTypeFixedString *>(arguments[1].get()))
			|| (right_tuple 		= typeid_cast<const DataTypeTuple *>(arguments[1].get()));

		const bool right_is_enum = right_is_enum8 || right_is_enum16;

		if (!(	(arguments[0]->behavesAsNumber() && arguments[1]->behavesAsNumber() && !(left_is_enum ^ right_is_enum))
			||	((left_is_string || left_is_fixed_string) && (right_is_string || right_is_fixed_string))
			||	(left_is_date && right_is_date)
			||	(left_is_date && right_is_string)	/// Можно сравнивать дату, дату-с-временем и перечисление с константной строкой.
			||	(left_is_string && right_is_date)
			||	(left_is_date_time && right_is_date_time)
			||	(left_is_date_time && right_is_string)
			||	(left_is_string && right_is_date_time)
			||	(left_is_date_time && right_is_date_time)
			||	(left_is_date_time && right_is_string)
			||	(left_is_string && right_is_date_time)
			||	(left_is_enum && right_is_enum && arguments[0]->getName() == arguments[1]->getName()) /// only equivalent enum type values can be compared against
			||	(left_is_enum && right_is_string)
			||	(left_is_string && right_is_enum)
			||	(left_tuple && right_tuple && left_tuple->getElements().size() == right_tuple->getElements().size())))
			throw Exception("Illegal types of arguments (" + arguments[0]->getName() + ", " + arguments[1]->getName() + ")"
				" of function " + getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);

		if (left_tuple && right_tuple)
		{
			size_t size = left_tuple->getElements().size();
			for (size_t i = 0; i < size; ++i)
				getReturnType({ left_tuple->getElements()[i], right_tuple->getElements()[i] });
		}

		return std::make_shared<DataTypeUInt8>();
	}

	/// Выполнить функцию над блоком.
	void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override
	{
		const auto & col_with_type_and_name_left = block.getByPosition(arguments[0]);
		const auto & col_with_type_and_name_right = block.getByPosition(arguments[1]);
		const IColumn * col_left_untyped = col_with_type_and_name_left.column.get();
		const IColumn * col_right_untyped = col_with_type_and_name_right.column.get();

		const bool left_is_num = col_left_untyped->isNumeric();
		const bool right_is_num = col_right_untyped->isNumeric();

		if (left_is_num && right_is_num)
		{
			if (!(	executeNumLeftType<UInt8>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<UInt16>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<UInt32>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<UInt64>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<Int8>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<Int16>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<Int32>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<Int64>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<Float32>(block, result, col_left_untyped, col_right_untyped)
				||	executeNumLeftType<Float64>(block, result, col_left_untyped, col_right_untyped)))
				throw Exception("Illegal column " + col_left_untyped->getName()
					+ " of first argument of function " + getName(),
					ErrorCodes::ILLEGAL_COLUMN);
		}
		else if (typeid_cast<const DataTypeTuple *>(col_with_type_and_name_left.type.get()))
			executeTuple(block, result, col_left_untyped, col_right_untyped);
		else if (!left_is_num && !right_is_num)
			executeString(block, result, col_left_untyped, col_right_untyped);
		else
			executeDateOrDateTimeOrEnumWithConstString(
				block, result, col_left_untyped, col_right_untyped,
				col_with_type_and_name_left.type, col_with_type_and_name_right.type,
				left_is_num, right_is_num);
}
};


using FunctionEquals = FunctionComparison<EqualsOp, 			NameEquals>			;
using FunctionNotEquals = FunctionComparison<NotEqualsOp, 		NameNotEquals>		;
using FunctionLess = FunctionComparison<LessOp, 				NameLess>			;
using FunctionGreater = FunctionComparison<GreaterOp, 			NameGreater>		;
using FunctionLessOrEquals = FunctionComparison<LessOrEqualsOp, 		NameLessOrEquals>	;
using FunctionGreaterOrEquals = FunctionComparison<GreaterOrEqualsOp,	NameGreaterOrEquals>;

}