ClickHouse/src/Core/NamesAndAliases.h

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#pragma once
#include <map>
#include <list>
#include <optional>
#include <string>
#include <set>
#include <initializer_list>
#include <DataTypes/IDataType.h>
#include <Core/Names.h>
namespace DB
{
class NameAndAliasPair
{
public:
NameAndAliasPair(const String & name_, const DataTypePtr & type_, const String & expression_)
: name(name_)
, type(type_)
, expression(expression_)
{}
String name;
DataTypePtr type;
String expression;
};
/// This needed to use structured bindings for NameAndTypePair
/// const auto & [name, type] = name_and_type
template <int I>
decltype(auto) get(const NameAndAliasPair & name_and_alias)
{
if constexpr (I == 0)
return name_and_alias.name;
else if constexpr (I == 1)
return name_and_alias.type;
else if constexpr (I == 2)
return name_and_alias.expression;
}
using NamesAndAliases = std::vector<NameAndAliasPair>;
}
namespace std
{
template <> struct tuple_size<DB::NameAndAliasPair> : std::integral_constant<size_t, 2> {};
template <> struct tuple_element<0, DB::NameAndAliasPair> { using type = DB::String; };
template <> struct tuple_element<1, DB::NameAndAliasPair> { using type = DB::DataTypePtr; };
template <> struct tuple_element<2, DB::NameAndAliasPair> { using type = DB::String; };
}