HashFunc函数——hash_group(key)

hash_group(key)

描述：流引擎中，该函数可将Group Clause中的各列计算为一个hash值。

参数：key为Group Clause中各列的值。

返回值类型：32位hash值

示例：

按照步骤依次执行。
openGauss=# CREATE TABLE tt(a int, b int,c int,d int);
NOTICE:  The 'DISTRIBUTE BY' clause is not specified. Using 'a' as the distribution column by default.
HINT:  Please use 'DISTRIBUTE BY' clause to specify suitable data distribution column.
CREATE TABLE
openGauss=# select * from tt;
 a | b | c | d 
---+---+---+---
(0 rows)
    
openGauss=# insert into tt values(1,2,3,4);
INSERT 0 1
openGauss=# select * from tt;
 a | b | c | d 
---+---+---+---
 1 | 2 | 3 | 4
(1 row)
    
openGauss=# insert into tt values(5,6,7,8);
INSERT 0 1
openGauss=# select * from tt;
 a | b | c | d 
---+---+---+---
 1 | 2 | 3 | 4
 5 | 6 | 7 | 8
(2 rows)
    
openGauss=# select hash_group(a,b) from tt where a=1 and b=2;
 hash_group 
------------
  990882385
(1 row)