You have to provide the following information whenever possible.

**Describe the bug**
This query fails with the latest stable version 21.5.5.12. It worked with the last stable version 21.4.7.3.

**Does it reproduce on recent release?**
yes

**How to reproduce**
21.5.5.12

```
SELECT
    label,
    number
FROM
(
    SELECT
        'a' AS label,
        number
    FROM
    (
        SELECT number
        FROM numbers(10)
    )
    UNION ALL
    SELECT
        'b' AS label,
        number
    FROM
    (
        SELECT number
        FROM numbers(10)
    )
)
WHERE number IN
(
    SELECT number
    FROM numbers(5)
)
```

**Expected behavior**
Query should run without errors

**Error message and/or stacktrace**
```
Received exception from server (version 21.5.5):
Code: 49. DB::Exception: Received from localhost:9000. DB::Exception: Block structure mismatch in Pipe::unitePipes stream: different names of columns:
label String String(size = 0), number UInt64 UInt64(size = 0), 'b' String Const(size = 0, String(size = 1))
label String String(size = 0), number UInt64 UInt64(size = 0), 'a' String Const(size = 0, String(size = 1)).
```

}
            else
            {
                dst_node = &actions_dag->addAlias(*dst_node, res_elem.name);
                projection[result_col_num] = dst_node;
            }
        }
        else
        {
            projection[result_col_num] = dst_node;
        }
    }
    actions_dag->index.swap(projection);
    actions_dag->removeUnusedActions();
    actions_dag->projectInput();
    return actions_dag;
}
ActionsDAGPtr ActionsDAG::makeAddingColumnActions(ColumnWithTypeAndName column)
{
    auto adding_column_action = std::make_shared<ActionsDAG>();
    FunctionOverloadResolverPtr func_builder_materialize = std::make_unique<FunctionToOverloadResolverAdaptor>(std::make_shared<FunctionMaterialize>());
    auto column_name = column.name;
    const auto * column_node = &adding_column_action->addColumn(std::move(column));
    NodeRawConstPtrs inputs = {column_node};
    const auto & function_node = adding_column_action->addFunction(func_builder_materialize, std::move(inputs), {});
    const auto & alias_node = adding_column_action->addAlias(function_node, std::move(column_name));
    adding_column_action->index.push_back(&alias_node);
    return adding_column_action;
}
ActionsDAGPtr ActionsDAG::merge(ActionsDAG && first, ActionsDAG && second)