```
select tupleElement(CAST(tuple(1,2),'Tuple(x UInt64, y UInt64)'), 'x') 
-- ok

select tupleElement(CAST(tuple(1,2),'Tuple(x UInt64, y UInt64)'), 'z')

-- fails
-- Code: 10. DB::Exception: Received from localhost:9000. DB::Exception: Tuple doesn't have element with name 'z': While processing tupleElement(CAST((1, 2), 'Tuple(x UInt64, y UInt64)'), 'z'). (NOT_FOUND_COLUMN_IN_BLOCK)
```
Proposal - add the 3rd parameter to the tupleElement function and return it if tuple doesn't have a member.

Why? Tuple comes from object('JSON'), sometimes some fields are missing in some jsons.
{
    
    size_t old_size = column.size();
    try
    {
        impl();
        
        size_t new_size = column.size();
        for (auto i : collections::range(0, elems.size()))
        {
            const auto & element_column = extractElementColumn(column, i);
            if (element_column.size() != new_size)
            {
                
                
                throw Exception(ErrorCodes::SIZES_OF_COLUMNS_IN_TUPLE_DOESNT_MATCH,
                    "Cannot read a tuple because not all elements are present");
            }
        }
    }
    catch (...)
    {
        for (const auto & i : collections::range(0, elems.size()))
        {
            auto & element_column = extractElementColumn(column, i);
            if (element_column.size() > old_size)
                element_column.popBack(1);
        }
        throw;