the query result of intersect can be aggregated before intersect

## Enhancement
consider the case that
```
select id, value from a intersect select id, value from b
```

From mysql's doc(https://dev.mysql.com/doc/refman/9.0/en/intersect.html), if intersect means intersect distinct by default, so the above sql is the same as

```
select id, value from a group by id, value intersect select id, value from b group by id, value
```

if there is a lots of duplicate entries in table a and table b, this aggregation can help to improve the query performance a lot, and also save the memory usage a lot.

Even if user's query is
```
select id, value from a intersect all select id, value from b
```
The query can still be rewriten as
```
select id, value from a intersect all select id, value from b group by id, value
```