ClickHouse/dbms/src/Common/FieldVisitors.h

#pragma once

#include <Core/Field.h>
#include <Core/AccurateComparison.h>
#include <common/demangle.h>


class SipHash;


namespace DB
{

namespace ErrorCodes
{
    extern const int CANNOT_CONVERT_TYPE;
    extern const int BAD_TYPE_OF_FIELD;
    extern const int LOGICAL_ERROR;
}

UInt128 stringToUUID(const String &);


/** StaticVisitor (and its descendants) - class with overloaded operator() for all types of fields.
  * You could call visitor for field using function 'applyVisitor'.
  * Also "binary visitor" is supported - its operator() takes two arguments.
  */
template <typename R = void>
struct StaticVisitor
{
    using ResultType = R;
};


/// F is template parameter, to allow universal reference for field, that is useful for const and non-const values.
template <typename Visitor, typename F>
typename std::decay_t<Visitor>::ResultType applyVisitor(Visitor && visitor, F && field)
{
    switch (field.getType())
    {
        case Field::Types::Null: return visitor(field.template get<Null>());
        case Field::Types::UInt64: return visitor(field.template get<UInt64>());
        case Field::Types::UInt128: return visitor(field.template get<UInt128>());
        case Field::Types::Int64: return visitor(field.template get<Int64>());
        case Field::Types::Float64: return visitor(field.template get<Float64>());
        case Field::Types::String: return visitor(field.template get<String>());
        case Field::Types::Array: return visitor(field.template get<Array>());
        case Field::Types::Tuple: return visitor(field.template get<Tuple>());
        case Field::Types::Decimal32: return visitor(field.template get<DecimalField<Decimal32>>());
        case Field::Types::Decimal64: return visitor(field.template get<DecimalField<Decimal64>>());
        case Field::Types::Decimal128: return visitor(field.template get<DecimalField<Decimal128>>());

        default:
            throw Exception("Bad type of Field", ErrorCodes::BAD_TYPE_OF_FIELD);
    }
}


template <typename Visitor, typename F1, typename F2>
static typename std::decay_t<Visitor>::ResultType applyBinaryVisitorImpl(Visitor && visitor, F1 && field1, F2 && field2)
{
    switch (field2.getType())
    {
        case Field::Types::Null:    return visitor(field1, field2.template get<Null>());
        case Field::Types::UInt64:  return visitor(field1, field2.template get<UInt64>());
        case Field::Types::UInt128: return visitor(field1, field2.template get<UInt128>());
        case Field::Types::Int64:   return visitor(field1, field2.template get<Int64>());
        case Field::Types::Float64: return visitor(field1, field2.template get<Float64>());
        case Field::Types::String:  return visitor(field1, field2.template get<String>());
        case Field::Types::Array:   return visitor(field1, field2.template get<Array>());
        case Field::Types::Tuple:   return visitor(field1, field2.template get<Tuple>());
        case Field::Types::Decimal32:  return visitor(field1, field2.template get<DecimalField<Decimal32>>());
        case Field::Types::Decimal64:  return visitor(field1, field2.template get<DecimalField<Decimal64>>());
        case Field::Types::Decimal128: return visitor(field1, field2.template get<DecimalField<Decimal128>>());

        default:
            throw Exception("Bad type of Field", ErrorCodes::BAD_TYPE_OF_FIELD);
    }
}

template <typename Visitor, typename F1, typename F2>
typename std::decay_t<Visitor>::ResultType applyVisitor(Visitor && visitor, F1 && field1, F2 && field2)
{
    switch (field1.getType())
    {
        case Field::Types::Null:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<Null>(), std::forward<F2>(field2));
        case Field::Types::UInt64:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<UInt64>(), std::forward<F2>(field2));
        case Field::Types::UInt128:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<UInt128>(), std::forward<F2>(field2));
        case Field::Types::Int64:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<Int64>(), std::forward<F2>(field2));
        case Field::Types::Float64:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<Float64>(), std::forward<F2>(field2));
        case Field::Types::String:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<String>(), std::forward<F2>(field2));
        case Field::Types::Array:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<Array>(), std::forward<F2>(field2));
        case Field::Types::Tuple:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<Tuple>(), std::forward<F2>(field2));
        case Field::Types::Decimal32:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<DecimalField<Decimal32>>(), std::forward<F2>(field2));
        case Field::Types::Decimal64:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<DecimalField<Decimal64>>(), std::forward<F2>(field2));
        case Field::Types::Decimal128:
            return applyBinaryVisitorImpl(
                std::forward<Visitor>(visitor), field1.template get<DecimalField<Decimal128>>(), std::forward<F2>(field2));

        default:
            throw Exception("Bad type of Field", ErrorCodes::BAD_TYPE_OF_FIELD);
    }
}


/** Prints Field as literal in SQL query */
class FieldVisitorToString : public StaticVisitor<String>
{
public:
    String operator() (const Null & x) const;
    String operator() (const UInt64 & x) const;
    String operator() (const UInt128 & x) const;
    String operator() (const Int64 & x) const;
    String operator() (const Float64 & x) const;
    String operator() (const String & x) const;
    String operator() (const Array & x) const;
    String operator() (const Tuple & x) const;
    String operator() (const DecimalField<Decimal32> & x) const;
    String operator() (const DecimalField<Decimal64> & x) const;
    String operator() (const DecimalField<Decimal128> & x) const;
};


/** Print readable and unique text dump of field type and value. */
class FieldVisitorDump : public StaticVisitor<String>
{
public:
    String operator() (const Null & x) const;
    String operator() (const UInt64 & x) const;
    String operator() (const UInt128 & x) const;
    String operator() (const Int64 & x) const;
    String operator() (const Float64 & x) const;
    String operator() (const String & x) const;
    String operator() (const Array & x) const;
    String operator() (const Tuple & x) const;
    String operator() (const DecimalField<Decimal32> & x) const;
    String operator() (const DecimalField<Decimal64> & x) const;
    String operator() (const DecimalField<Decimal128> & x) const;
};


/** Converts numberic value of any type to specified type. */
template <typename T>
class FieldVisitorConvertToNumber : public StaticVisitor<T>
{
public:
    T operator() (const Null &) const
    {
        throw Exception("Cannot convert NULL to " + demangle(typeid(T).name()), ErrorCodes::CANNOT_CONVERT_TYPE);
    }

    T operator() (const String &) const
    {
        throw Exception("Cannot convert String to " + demangle(typeid(T).name()), ErrorCodes::CANNOT_CONVERT_TYPE);
    }

    T operator() (const Array &) const
    {
        throw Exception("Cannot convert Array to " + demangle(typeid(T).name()), ErrorCodes::CANNOT_CONVERT_TYPE);
    }

    T operator() (const Tuple &) const
    {
        throw Exception("Cannot convert Tuple to " + demangle(typeid(T).name()), ErrorCodes::CANNOT_CONVERT_TYPE);
    }

    T operator() (const UInt64 & x) const { return x; }
    T operator() (const Int64 & x) const { return x; }
    T operator() (const Float64 & x) const { return x; }

    T operator() (const UInt128 &) const
    {
        throw Exception("Cannot convert UInt128 to " + demangle(typeid(T).name()), ErrorCodes::CANNOT_CONVERT_TYPE);
    }

    template <typename U>
    T operator() (const DecimalField<U> & x) const
    {
        if constexpr (std::is_floating_point_v<T>)
            return static_cast<T>(x.getValue()) / x.getScaleMultiplier();
        else
            return x.getValue() / x.getScaleMultiplier();
    }
};


/** Updates SipHash by type and value of Field */
class FieldVisitorHash : public StaticVisitor<>
{
private:
    SipHash & hash;
public:
    FieldVisitorHash(SipHash & hash);

    void operator() (const Null & x) const;
    void operator() (const UInt64 & x) const;
    void operator() (const UInt128 & x) const;
    void operator() (const Int64 & x) const;
    void operator() (const Float64 & x) const;
    void operator() (const String & x) const;
    void operator() (const Array & x) const;
    void operator() (const DecimalField<Decimal32> & x) const;
    void operator() (const DecimalField<Decimal64> & x) const;
    void operator() (const DecimalField<Decimal128> & x) const;
};


template <typename T> constexpr bool isDecimalField() { return false; }
template <> constexpr bool isDecimalField<DecimalField<Decimal32>>() { return true; }
template <> constexpr bool isDecimalField<DecimalField<Decimal64>>() { return true; }
template <> constexpr bool isDecimalField<DecimalField<Decimal128>>() { return true; }


/** More precise comparison, used for index.
  * Differs from Field::operator< and Field::operator== in that it also compares values of different types.
  * Comparison rules are same as in FunctionsComparison (to be consistent with expression evaluation in query).
  */
class FieldVisitorAccurateEquals : public StaticVisitor<bool>
{
public:
    bool operator() (const UInt64 & l, const Null & r)      const { return cantCompare(l, r); }
    bool operator() (const UInt64 & l, const UInt64 & r)    const { return l == r; }
    bool operator() (const UInt64 & l, const UInt128 & r)   const { return cantCompare(l, r); }
    bool operator() (const UInt64 & l, const Int64 & r)     const { return accurate::equalsOp(l, r); }
    bool operator() (const UInt64 & l, const Float64 & r)   const { return accurate::equalsOp(l, r); }
    bool operator() (const UInt64 & l, const String & r)    const { return cantCompare(l, r); }
    bool operator() (const UInt64 & l, const Array & r)     const { return cantCompare(l, r); }
    bool operator() (const UInt64 & l, const Tuple & r)     const { return cantCompare(l, r); }

    bool operator() (const Int64 & l, const Null & r)       const { return cantCompare(l, r); }
    bool operator() (const Int64 & l, const UInt64 & r)     const { return accurate::equalsOp(l, r); }
    bool operator() (const Int64 & l, const UInt128 & r)    const { return cantCompare(l, r); }
    bool operator() (const Int64 & l, const Int64 & r)      const { return l == r; }
    bool operator() (const Int64 & l, const Float64 & r)    const { return accurate::equalsOp(l, r); }
    bool operator() (const Int64 & l, const String & r)     const { return cantCompare(l, r); }
    bool operator() (const Int64 & l, const Array & r)      const { return cantCompare(l, r); }
    bool operator() (const Int64 & l, const Tuple & r)      const { return cantCompare(l, r); }

    bool operator() (const Float64 & l, const Null & r)     const { return cantCompare(l, r); }
    bool operator() (const Float64 & l, const UInt64 & r)   const { return accurate::equalsOp(l, r); }
    bool operator() (const Float64 & l, const UInt128 & r)  const { return cantCompare(l, r); }
    bool operator() (const Float64 & l, const Int64 & r)    const { return accurate::equalsOp(l, r); }
    bool operator() (const Float64 & l, const Float64 & r)  const { return l == r; }
    bool operator() (const Float64 & l, const String & r)   const { return cantCompare(l, r); }
    bool operator() (const Float64 & l, const Array & r)    const { return cantCompare(l, r); }
    bool operator() (const Float64 & l, const Tuple & r)    const { return cantCompare(l, r); }

    template <typename T>
    bool operator() (const Null &, const T &) const
    {
        return std::is_same_v<T, Null>;
    }

    template <typename T>
    bool operator() (const String & l, const T & r) const
    {
        if constexpr (std::is_same_v<T, String>)
            return l == r;
        if constexpr (std::is_same_v<T, UInt128>)
            return stringToUUID(l) == r;
        return cantCompare(l, r);
    }

    template <typename T>
    bool operator() (const UInt128 & l, const T & r) const
    {
        if constexpr (std::is_same_v<T, UInt128>)
            return l == r;
        if constexpr (std::is_same_v<T, String>)
            return l == stringToUUID(r);
        return cantCompare(l, r);
    }

    template <typename T>
    bool operator() (const Array & l, const T & r) const
    {
        if constexpr (std::is_same_v<T, Array>)
            return l == r;
        return cantCompare(l, r);
    }

    template <typename T>
    bool operator() (const Tuple & l, const T & r) const
    {
        if constexpr (std::is_same_v<T, Tuple>)
            return l == r;
        return cantCompare(l, r);
    }

    template <typename T, typename U>
    bool operator() (const DecimalField<T> & l, const U & r) const
    {
        if constexpr (isDecimalField<U>())
            return l == r;
        if constexpr (std::is_same_v<U, Int64> || std::is_same_v<U, UInt64>)
            return l == DecimalField<Decimal128>(r, 0);
        return cantCompare(l, r);
    }

    template <typename T> bool operator() (const UInt64 & l, const DecimalField<T> & r) const { return DecimalField<Decimal128>(l, 0) == r; }
    template <typename T> bool operator() (const Int64 & l, const DecimalField<T> & r) const { return DecimalField<Decimal128>(l, 0) == r; }
    template <typename T> bool operator() (const Float64 & l, const DecimalField<T> & r) const { return cantCompare(l, r); }

private:
    template <typename T, typename U>
    bool cantCompare(const T &, const U &) const
    {
        if constexpr (std::is_same_v<U, Null>)
            return false;
        throw Exception("Cannot compare " + demangle(typeid(T).name()) + " with " + demangle(typeid(U).name()),
                        ErrorCodes::BAD_TYPE_OF_FIELD);
    }
};


class FieldVisitorAccurateLess : public StaticVisitor<bool>
{
public:
    bool operator() (const UInt64 & l, const Null & r)      const { return cantCompare(l, r); }
    bool operator() (const UInt64 & l, const UInt64 & r)    const { return l < r; }
    bool operator() (const UInt64 & l, const UInt128 & r)   const { return cantCompare(l, r); }
    bool operator() (const UInt64 & l, const Int64 & r)     const { return accurate::lessOp(l, r); }
    bool operator() (const UInt64 & l, const Float64 & r)   const { return accurate::lessOp(l, r); }
    bool operator() (const UInt64 & l, const String & r)    const { return cantCompare(l, r); }
    bool operator() (const UInt64 & l, const Array & r)     const { return cantCompare(l, r); }
    bool operator() (const UInt64 & l, const Tuple & r)     const { return cantCompare(l, r); }

    bool operator() (const Int64 & l, const Null & r)       const { return cantCompare(l, r); }
    bool operator() (const Int64 & l, const UInt64 & r)     const { return accurate::lessOp(l, r); }
    bool operator() (const Int64 & l, const UInt128 & r)    const { return cantCompare(l, r); }
    bool operator() (const Int64 & l, const Int64 & r)      const { return l < r; }
    bool operator() (const Int64 & l, const Float64 & r)    const { return accurate::lessOp(l, r); }
    bool operator() (const Int64 & l, const String & r)     const { return cantCompare(l, r); }
    bool operator() (const Int64 & l, const Array & r)      const { return cantCompare(l, r); }
    bool operator() (const Int64 & l, const Tuple & r)      const { return cantCompare(l, r); }

    bool operator() (const Float64 & l, const Null & r)     const { return cantCompare(l, r); }
    bool operator() (const Float64 & l, const UInt64 & r)   const { return accurate::lessOp(l, r); }
    bool operator() (const Float64 & l, const UInt128 & r)  const { return cantCompare(l, r); }
    bool operator() (const Float64 & l, const Int64 & r)    const { return accurate::lessOp(l, r); }
    bool operator() (const Float64 & l, const Float64 & r)  const { return l < r; }
    bool operator() (const Float64 & l, const String & r)   const { return cantCompare(l, r); }
    bool operator() (const Float64 & l, const Array & r)    const { return cantCompare(l, r); }
    bool operator() (const Float64 & l, const Tuple & r)    const { return cantCompare(l, r); }

    template <typename T>
    bool operator() (const Null &, const T &) const
    {
        return !std::is_same_v<T, Null>;
    }

    template <typename T>
    bool operator() (const String & l, const T & r) const
    {
        if constexpr (std::is_same_v<T, String>)
            return l < r;
        if constexpr (std::is_same_v<T, UInt128>)
            return stringToUUID(l) < r;
        return cantCompare(l, r);
    }

    template <typename T>
    bool operator() (const UInt128 & l, const T & r) const
    {
        if constexpr (std::is_same_v<T, UInt128>)
            return l < r;
        if constexpr (std::is_same_v<T, String>)
            return l < stringToUUID(r);
        return cantCompare(l, r);
    }

    template <typename T>
    bool operator() (const Array & l, const T & r) const
    {
        if constexpr (std::is_same_v<T, Array>)
            return l < r;
        return cantCompare(l, r);
    }

    template <typename T>
    bool operator() (const Tuple & l, const T & r) const
    {
        if constexpr (std::is_same_v<T, Tuple>)
            return l < r;
        return cantCompare(l, r);
    }

    template <typename T, typename U>
    bool operator() (const DecimalField<T> & l, const U & r) const
    {
        if constexpr (isDecimalField<U>())
            return l < r;
        else if constexpr (std::is_same_v<U, Int64> || std::is_same_v<U, UInt64>)
            return l < DecimalField<Decimal128>(r, 0);
        return cantCompare(l, r);
    }

    template <typename T> bool operator() (const UInt64 & l, const DecimalField<T> & r) const { return DecimalField<Decimal128>(l, 0) < r; }
    template <typename T> bool operator() (const Int64 & l, const DecimalField<T> & r) const { return DecimalField<Decimal128>(l, 0) < r; }
    template <typename T> bool operator() (const Float64 &, const DecimalField<T> &) const { return false; }

private:
    template <typename T, typename U>
    bool cantCompare(const T &, const U &) const
    {
        throw Exception("Cannot compare " + demangle(typeid(T).name()) + " with " + demangle(typeid(U).name()),
                        ErrorCodes::BAD_TYPE_OF_FIELD);
    }
};


/** Implements `+=` operation.
 *  Returns false if the result is zero.
 */
class FieldVisitorSum : public StaticVisitor<bool>
{
private:
    const Field & rhs;
public:
    explicit FieldVisitorSum(const Field & rhs_) : rhs(rhs_) {}

    bool operator() (UInt64 & x) const { x += get<UInt64>(rhs); return x != 0; }
    bool operator() (Int64 & x) const { x += get<Int64>(rhs); return x != 0; }
    bool operator() (Float64 & x) const { x += get<Float64>(rhs); return x != 0; }

    bool operator() (Null &) const { throw Exception("Cannot sum Nulls", ErrorCodes::LOGICAL_ERROR); }
    bool operator() (String &) const { throw Exception("Cannot sum Strings", ErrorCodes::LOGICAL_ERROR); }
    bool operator() (Array &) const { throw Exception("Cannot sum Arrays", ErrorCodes::LOGICAL_ERROR); }
    bool operator() (UInt128 &) const { throw Exception("Cannot sum UUIDs", ErrorCodes::LOGICAL_ERROR); }

    template <typename T>
    bool operator() (DecimalField<T> & x) const
    {
        x += get<DecimalField<T>>(rhs);
        return x.getValue() != 0;
    }
};

}