test
```sql
DROP TABLE IF EXISTS t;
DROP TABLE IF EXISTS t_mv;
create table t (a UInt64) Engine = Null;
create materialized view t_mv Engine = Null AS select now() as ts, max(a) from t group by ts;
insert into t select * from numbers_mt(3000000000) settings max_threads = 16, max_insert_threads=16;
```

results:
```
21.8:  
0 rows in set. Elapsed: 3.841 sec. Processed 3.00 billion rows, 24.00 GB (781.01 million rows/s., 6.25 GB/s.)

21.10: 
0 rows in set. Elapsed: 3.844 sec. Processed 6.00 billion rows, 48.00 GB (1.56 billion rows/s., 12.49 GB/s.)

21.11:
0 rows in set. Elapsed: 17.717 sec. Processed 5.98 billion rows, 47.86 GB (337.70 million rows/s., 2.70 GB/s.)

21.12
0 rows in set. Elapsed: 18.569 sec. Processed 6.00 billion rows, 48.00 GB (323.12 million rows/s., 2.58 GB/s.)

22.1
0 rows in set. Elapsed: 19.124 sec. Processed 6.00 billion rows, 48.00 GB (313.74 million rows/s., 2.51 GB/s.)

22.2
0 rows in set. Elapsed: 19.939 sec. Processed 6.00 billion rows, 48.00 GB (300.92 million rows/s., 2.41 GB/s.)

22.3
0 rows in set. Elapsed: 18.727 sec. Processed 6.00 billion rows, 48.00 GB (320.39 million rows/s., 2.56 GB/s.)

22.4
0 rows in set. Elapsed: 19.698 sec. Processed 6.00 billion rows, 48.00 GB (304.60 million rows/s., 2.44 GB/s.)

22.5
0 rows in set. Elapsed: 22.723 sec. Processed 6.00 billion rows, 48.00 GB (264.05 million rows/s., 2.11 GB/s.)
```

SIde note: pay attention to processed rows and progress bar behavior (minor cosmetic issue).
const auto & output_columns = metadata_snapshot->getColumns();
                if (input_columns.size() == query_columns.size())
                {
                    for (size_t col_idx = 0; col_idx < query_columns.size(); ++col_idx)
                    {
                        
                        
                        if (input_columns[col_idx].type->isNullable() && !query_columns[col_idx].type->isNullable() && output_columns.hasDefault(query_columns[col_idx].name))
                            query_sample_block.setColumn(col_idx, ColumnWithTypeAndName(makeNullable(query_columns[col_idx].column), makeNullable(query_columns[col_idx].type), query_columns[col_idx].name));
                    }
                }
            }
        }
        else if (query.watch)
        {
            InterpreterWatchQuery interpreter_watch{ query.watch, getContext() };
            pipeline = interpreter_watch.buildQueryPipeline();
        }
        for (size_t i = 0; i < out_streams_size; ++i)
        {
            auto out = buildChainImpl(table, metadata_snapshot, query_sample_block, nullptr, nullptr);
            out_chains.emplace_back(std::move(out));
        }
    }
    BlockIO res;
    
    if (distributed_pipeline)
    {
        res.pipeline = std::move(*distributed_pipeline);
    }