This pr mainly to optimize the histogram(👉🏻https://github.com/apache/doris/pull/14910) aggregation function. Including the following:
1. Support input parameters `sample_rate` and `max_bucket_num`
2. Add UT and regression test
3. Add documentation
4. Optimize function implementation logic
Parameter description：
- `sample_rate`：Optional. The proportion of sample data used to generate the histogram. The default is 0.2.
- `max_bucket_num`：Optional. Limit the number of histogram buckets. The default value is 128.
---
Example：
```
MySQL [test]> SELECT histogram(c_float) FROM histogram_test;
+-------------------------------------------------------------------------------------------------------------------------------------+
| histogram(`c_float`) |
+-------------------------------------------------------------------------------------------------------------------------------------+
| {"sample_rate":0.2,"max_bucket_num":128,"bucket_num":3,"buckets":[{"lower":"0.1","upper":"0.1","count":1,"pre_sum":0,"ndv":1},...]} |
+-------------------------------------------------------------------------------------------------------------------------------------+
MySQL [test]> SELECT histogram(c_string, 0.5, 2) FROM histogram_test;
+-------------------------------------------------------------------------------------------------------------------------------------+
| histogram(`c_string`) |
+-------------------------------------------------------------------------------------------------------------------------------------+
| {"sample_rate":0.5,"max_bucket_num":2,"bucket_num":2,"buckets":[{"lower":"str1","upper":"str7","count":4,"pre_sum":0,"ndv":3},...]} |
+-------------------------------------------------------------------------------------------------------------------------------------+
```
Query result description：
```
{
"sample_rate": 0.2,
"max_bucket_num": 128,
"bucket_num": 3,
"buckets": [
{
"lower": "0.1",
"upper": "0.2",
"count": 2,
"pre_sum": 0,
"ndv": 2
},
{
"lower": "0.8",
"upper": "0.9",
"count": 2,
"pre_sum": 2,
"ndv": 2
},
{
"lower": "1.0",
"upper": "1.0",
"count": 2,
"pre_sum": 4,
"ndv": 1
}
]
}
```
Field description：
- sample_rate：Rate of sampling
- max_bucket_num：Limit the maximum number of buckets
- bucket_num：The actual number of buckets
- buckets：All buckets
- lower：Upper bound of the bucket
- upper：Lower bound of the bucket
- count：The number of elements contained in the bucket
- pre_sum：The total number of elements in the front bucket
- ndv：The number of different values in the bucket
> Total number of histogram elements = number of elements in the last bucket(count) + total number of elements in the previous bucket(pre_sum).
MySQL [db]> SELECT SUM(a.r[1]) as active_user_num, SUM(a.r[2]) as active_user_num_1day, SUM(a.r[3]) as active_user_num_3day, SUM(a.r[4]) as active_user_num_7day FROM ( SELECT user_id, retention( day = '2022-11-01', day = '2022-11-02', day = '2022-11-04', day = '2022-11-07') as r FROM login_event WHERE (day >= '2022-11-01') AND (day <= '2022-11-21') GROUP BY user_id ) a;
ERROR 1105 (HY000): errCode = 2, detailMessage = sum requires a numeric parameter: sum(%element_extract%(a.r, 1))
in the previous, the result is:
```
mysql> select array_position([1, null], null);
+--------------------------------------+
| array_position(ARRAY(1, NULL), NULL) |
+--------------------------------------+
| NULL |
+--------------------------------------+
1 row in set (0.02 sec)
```
but after this commit, the result become:
```
mysql> select array_position([1, null], null);
+--------------------------------------+
| array_position(ARRAY(1, NULL), NULL) |
+--------------------------------------+
| 2 |
+--------------------------------------+
1 row in set (0.02 sec)
```
refractor DataTypeArray from_string, make it more clear;
support ',' and ']' inside string element, for example: ['hello,,,', 'world][]']
support empty elements, such as [,] ==> [0,0]
Co-authored-by: cambyzju <zhuxiaoli01@baidu.com>
