
```
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))
```
{
    Node * predicate = const_cast<Node *>(tryFindInIndex(filter_name));
    if (!predicate)
            throw Exception(ErrorCodes::LOGICAL_ERROR,
                            "Index for ActionsDAG does not contain filter column name {}. DAG:\n{}",
                            filter_name, dumpDAG());
    
    
    if (predicate->type == ActionType::COLUMN)
        return nullptr;
    std::unordered_set<const Node *> allowed_nodes;
    
    {
        std::unordered_map<std::string_view, std::list<const Node *>> inputs_map;
        for (const auto & input : inputs)
            inputs_map[input->result_name].emplace_back(input);
        for (const auto & name : available_inputs)
        {
            auto & inputs_list = inputs_map[name];
            if (inputs_list.empty())
                continue;
            allowed_nodes.emplace(inputs_list.front());
            inputs_list.pop_front();
        }
    }
    auto conjunction = getConjunctionNodes(predicate, allowed_nodes);
    auto actions = cloneActionsForConjunction(conjunction.allowed, all_inputs);
    if (!actions)
        return nullptr;