Fix: #3946
CL:
1. Add prepare phase for `from_unixtime()`, `date_format()` and `convert_tz()` functions, to handle the format string once for all.
2. Find the cctz timezone when init `runtime state`, so that don't need to find timezone for each rows.
3. Add constant rewrite rule for `utc_timestamp()`
4. Add doc for `to_date()`
5. Comment out the `push_handler_test`, it can not run in DEBUG mode, will be fixed later.
6. Remove `timezone_db.h/cpp` and add `timezone_utils.h/cpp`
The performance shows bellow:
11,000,000 rows
SQL1: `select count(from_unixtime(k1)) from tbl1;`
Before: 8.85s
After: 2.85s
SQL2: `select count(from_unixtime(k1, '%Y-%m-%d %H:%i:%s')) from tbl1 limit 1;`
Before: 10.73s
After: 4.85s
The date string format seems still slow, we may need a further enhancement about it.
* Support bitmap_intersect
Support aggregate function Bitmap Intersect, it is mainly used to take intersection of grouped data.
The function 'bitmap_intersect(expr)' calculates the intersection of bitmap columns and returns a bitmap object.
The defination is following:
FunctionName: bitmap_intersect,
InputType: bitmap,
OutputType: bitmap
The scenario is as follows:
Query which users satisfy the three tags a, b, and c at the same time.
```
select bitmap_to_string(bitmap_intersect(user_id)) from
(
select bitmap_union(user_id) user_id from bitmap_intersect_test
where tag in ('a', 'b', 'c')
group by tag
) a
```
Closed#3552.
* Add docs of bitmap_union and bitmap_intersect
* Support null of bitmap_intersect
