
```
select *
from (
select 'table' as table, toInt64(10) as rows, toInt64(101) as elements
union all
select 'another table' as table, toInt64(0) as rows, toInt64(0) as elements
)
where rows - elements <> 0

DB::Exception: Block structure mismatch in Pipe::unitePipes stream: different number of columns:
table String String(size = 0), rows Int64 Int64(size = 0), elements Int64 Int64(size = 0)
table String String(size = 0), rows Int64 Int64(size = 0), elements Int64 Int64(size = 0), dummy UInt8 UInt8(size = 0) (version 21.5.3.1 (official build))
```
}
    
    auto it = inputs.begin();
    for (; it != inputs.end(); ++it)
        if (*it == col)
            break;
    if (it == inputs.end())
        return false;
    
    for (const auto & node : nodes)
        for (const auto * child : node.children)
            if (col == child)
                return false;
    
    for (const auto * node : index)
        if (col == node)
            return false;
    
    for (auto jt = nodes.begin(); jt != nodes.end(); ++jt)
    {
        if (&(*jt) == *it)
        {
            nodes.erase(jt);
            break;
        }
    }
    inputs.erase(it);
    return true;
}
ActionsDAGPtr ActionsDAG::clone() const