
```
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))
```
if (it != inputs_map.end())
                node = it->second;
        }
    }
    
    if (second.project_input)
    {
        first.index.swap(second.index);
        first.project_input = true;
    }
    else
    {
        
        for (const auto * node : first.index)
        {
            auto it = removed_first_result.find(node);
            if (it != removed_first_result.end() && it->second > 0)
                --it->second;
            else
                second.index.push_back(node);
        }
        first.index.swap(second.index);
    }
    first.nodes.splice(first.nodes.end(), std::move(second.nodes));
    first.projected_output = second.projected_output;
    
    first.removeUnusedActions();
    return std::make_shared<ActionsDAG>(std::move(first));
}
ActionsDAG::SplitResult ActionsDAG::split(std::unordered_set<const Node *> split_nodes) const