Hash Function
- hash_array(anyarray)
Description: Hashes an array, obtains the result of an array element using the hash function, and returns the combination result.
Parameter: data of the anyarray type
Return type: integer
Example:
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openGauss=# select hash_array(ARRAY[[1,2,3],[1,2,3]]); hash_array ------------ -382888479 (1 row)
- hash_group(key)
Description: Calculates the hash value of each column in the Group Clause in the streaming engine. (Due to specification changes, the current version no longer supports the current feature. Do not use this feature.)
Parameter: key indicates the value of each column in the Group Clause.
Return type: 32-bit hash value
Example:
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Perform the following steps in sequence. 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)
- hash_numeric(numeric)
Description: Calculates the hash value of numeric data.
Parameter: data of the numeric type.
Return type: integer
Example:
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openGauss=# select hash_numeric(30); hash_numeric -------------- -282860963 (1 row)
- hash_range(anyrange)
Description: Calculates the hash value of a range.
Parameter: data of the anyrange type
Return type: integer
Example:
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openGauss=# select hash_range(numrange(1.1,2.2)); hash_range ------------ 683508754 (1 row)
- hashbpchar(character)
Description: Calculates the hash value of bpchar.
Parameter: data of the character type
Return type: integer
Example:
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openGauss=# select hashbpchar('hello'); hashbpchar ------------- -1870292951 (1 row)
- hashchar(char)
Description: Converts char and Boolean data into hash values.
Parameter: data of the char or bool type
Return type: integer
Example:
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openGauss=# select hashbpchar('hello'); hashbpchar ------------- -1870292951 (1 row) openGauss=# select hashchar('true'); hashchar ------------ 1686226652 (1 row)
- hashenum(anyenum)
Description: Converts enumerated values to hash values.
Parameter: data of the anyenum type
Return type: integer
Example:
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openGauss=# CREATE TYPE b1 AS ENUM('good', 'bad', 'ugly'); CREATE TYPE openGauss=# call hashenum('good'::b1); hashenum ------------ 1821213359 (1 row)
- hashfloat4(real)
Description: Converts float4 values to hash values.
Parameter: data of the real type
Return type: integer
Example:
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openGauss=# select hashfloat4(12.1234); hashfloat4 ------------ 1398514061 (1 row)
- hashfloat8(double precision)
Description: Converts float8 values to hash values.
Parameter: data of the double precision type
Return type: integer
Example:
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openGauss=# select hashfloat8(123456.1234); hashfloat8 ------------ 1673665593 (1 row)
- hashinet(inet)
Description: Supports hashing indexes on inet or cidr. Returns the hash value of inet.
Parameter: data of the inet type
Return type: integer
Example:
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openGauss=# select hashinet('127.0.0.1'::inet); hashinet ------------- -1435793109 (1 row)
- hashint1(tinyint)
Description: Converts INT1 values to hash values.
Parameter: data of the tinyint type
Return type: uint32
Example:
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openGauss=# select hashint1(20); hashint1 ------------- -2014641093 (1 row)
- hashint2(smallint)
Description: Converts INT2 values to hash values.
Parameter: data of the smallint type
Return type: uint32
Example:
openGauss=# select hashint2(20000); hashint2 ------------ -863179081 (1 row)
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