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.
Currently we choose BE random without check disk is available,
the create table will failed until create tablet task is sent to BE
and BE will check is there has available capacity to create tablet.
So check backend disk available by storage medium will reduce unnecessary RPC call.
* 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
