MergeProcessor should respect the origin source order

[sundy-li]

mysql> select number from system.numbers_mt(20) limit 3;
+--------+
| number |
+--------+
|      0 |
|      1 |
|      4 |
+--------+
3 rows in set (0.00 sec)

[BohuTANG]

Yes.
But it's hard to do without order by clause, any ideas?

[sundy-li]

Just use vector instead of channel by default?

[BohuTANG]

Merge processor is dependened on the tokio scheduler(spawn), I think the sequence of merge processor is not the place to rush to solve, fuse-query will do limit push down later, then the result is make sense.