feat(agg_func): Add QUANTILE_DISC, KURTOSIS, SKEWNESS aggregate functions (#10886)

Author: ariesdevil

docs/doc/15-sql-functions/10-aggregate-functions/aggregate-kurtosis.md

@@ -0,0 +1,49 @@
+---
+title: KURTOSIS
+---
+
+Aggregate function.
+
+The `KURTOSIS()` function returns the excess kurtosis of all input values.
+
+## Syntax
+
+```sql
+KURTOSIS(expression)
+```
+
+## Arguments
+
+| Arguments   | Description                     |
+| ----------- | -----------                     |
+| expression  | Any numerical expression        |
+
+## Return Type
+
+Nullable Float64.
+
+## Examples
+
+```sql
+create table aggr(k int, v int, v2 int null);
+
+insert into aggr values
+    (1, 10, null),
+    (2, 10, 11),
+    (2, 10, 15),
+    (2, 10, 18),
+    (2, 20, 22),
+    (2, 20, 25),
+    (2, 25, null),
+    (2, 30, 35),
+    (2, 30, 40),
+    (2, 30, 50),
+    (2, 30, 51);
+
+select kurtosis(k), kurtosis(v), kurtosis(v2) from aggr;
++-------------------+---------------------+---------------------+
+| kurtosis(k)       | kurtosis(v)         | kurtosis(v2)        |
++-------------------+---------------------+---------------------+
+| 10.99999999999836 | -1.9614277138467147 | -1.4451196915855287 |
++-------------------+---------------------+---------------------+
+```

docs/doc/15-sql-functions/10-aggregate-functions/aggregate-quantile-cont.md

@@ -0,0 +1,55 @@
+---
+title: QUANTILE_CONT
+---
+
+Aggregate function.
+
+The QUANTILE_CONT() function computes the interpolated quantile number of a numeric data sequence.
+
+:::caution
+NULL values are not counted.
+:::
+
+## Syntax
+
+```sql
+QUANTILE_CONT(level)(expression)
+    
+QUANTILE_CONT(level1, level2, ...)(expression)
+```
+
+## Arguments
+
+| Arguments   | Description                                                                                                                                   |
+|-------------|-----------------------------------------------------------------------------------------------------------------------------------------------|
+| level(s)    | level(s) of quantile. Each level is constant floating-point number from 0 to 1. We recommend using a level value in the range of [0.01, 0.99] |
+| ----------- | -----------                                                                                                                                   |
+| expression  | Any numerical expression                                                                                                                      |
+
+## Return Type
+
+Float64 or float64 array based on level number.
+
+## Examples
+
+:::tip
+QUANTILE_CONT(0.6)(N) – A table for test with the single `number` column (UInt64) that contains integers from 0 to N-1.
+:::
+
+```sql
+SELECT QUANTILE_CONT(0.6)(number) FROM numbers(10000);
++----------------------------+
+| quantile_cont(0.6)(number) |
++----------------------------+
+|       5999.4               |
++----------------------------+
+```
+
+```sql
+SELECT QUANTILE_CONT(0, 0.5, 0.6, 1)(number) FROM numbers_mt(10000);
++---------------------------------------+
+| quantile_cont(0, 0.5, 0.6, 1)(number) |
++---------------------------------------+
+|      [0.0,4999.5,5999.4,9999.0]       |
++---------------------------------------+
+```

docs/doc/15-sql-functions/10-aggregate-functions/aggregate-quantile.md

@@ -1,10 +1,11 @@
 ---
-title: QUANTILE
+title: QUANTILE_DISC
 ---
 
 Aggregate function.
 
-The QUANTILE_CONT() function computes the interpolated quantile number of a numeric data sequence.
+The `QUANTILE_DISC()` function computes the exact quantile number of a numeric data sequence.
+The `QUANTILE` alias to `QUANTILE_DISC`
 
 :::caution
 NULL values are not counted.
@@ -13,9 +14,9 @@ NULL values are not counted.
 ## Syntax
 
 ```sql
-QUANTILE_CONT(level)(expression)
+QUANTILE_DISC(level)(expression)
 
-QUANTILE_CONT(level1, level2, ...)(expression)
+QUANTILE_DISC(level1, level2, ...)(expression)
 ```
 
 ## Arguments
@@ -28,28 +29,28 @@ QUANTILE_CONT(level1, level2, ...)(expression)
 
 ## Return Type
 
-Float64 or float64 array based on level number.
+InputType or array of InputType based on level number.
 
 ## Examples
 
 :::tip
-QUANTILE_CONT(0.6)(N) – A table for test with the single `number` column (UInt64) that contains integers from 0 to N-1.
+QUANTILE_DISC(0.6)(N) – A table for test with the single `number` column (UInt64) that contains integers from 0 to N-1.
 :::
 
 ```sql
-SELECT QUANTILE_CONT(0.6)(number) FROM numbers(10000);
+SELECT QUANTILE_DISC(0.6)(number) FROM numbers(10000);
 +----------------------------+
-| quantile_cont(0.6)(number) |
+| QUANTILE_DISC(0.6)(number) |
 +----------------------------+
-|       5999.4               |
+|       5999                 |
 +----------------------------+
 ```
 
 ```sql
-SELECT QUANTILE_CONT(0, 0.5, 0.6, 1)(number) FROM numbers_mt(10000);
+SELECT QUANTILE_DISC(0, 0.5, 0.6, 1)(number) FROM numbers_mt(10000);
 +---------------------------------------+
-| quantile_cont(0, 0.5, 0.6, 1)(number) |
+| QUANTILE_DISC(0, 0.5, 0.6, 1)(number) |
 +---------------------------------------+
-|      [0.0,4999.5,5999.4,9999.0]       |
+|      [0, 4999 ,5999 ,9999 ]           |
 +---------------------------------------+
 ```

docs/doc/15-sql-functions/10-aggregate-functions/aggregate-skewness.md

@@ -0,0 +1,49 @@
+---
+title: SKEWNESS
+---
+
+Aggregate function.
+
+The `SKEWNESS()` function returns the skewness of all input values.
+
+## Syntax
+
+```sql
+SKEWNESS(expression)
+```
+
+## Arguments
+
+| Arguments   | Description                     |
+| ----------- | -----------                     |
+| expression  | Any numerical expression        |
+
+## Return Type
+
+Nullable Float64.
+
+## Examples
+
+```sql
+create table aggr(k int, v int, v2 int null);
+
+insert into aggr values
+    (1, 10, null),
+    (2, 10, 11),
+    (2, 10, 15),
+    (2, 10, 18),
+    (2, 20, 22),
+    (2, 20, 25),
+    (2, 25, null),
+    (2, 30, 35),
+    (2, 30, 40),
+    (2, 30, 50),
+    (2, 30, 51);
+
+select skewness(k), skewness(v), skewness(v2) from aggr;
++--------------------+----------------------+--------------------+
+| skewness(k)        | skewness(v)          | skewness(v2)       |
++--------------------+----------------------+--------------------+
+| -3.316624790355393 | -0.16344366935199225 | 0.3654008511025841 |
++--------------------+----------------------+--------------------+
+```