Hash Function
- bucketabstime (value, flag)
Description: Hashes the value in the abstime format and finds the corresponding hash bucket.
Parameter: value indicates the value to be converted, which is of the abstime type. flag is of the int type, indicating the data distribution mode. The value 0 indicates hash distribution.
Return type: int32
Example:
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openGauss=# select bucketabstime('2011-10-01 10:10:10.112',1); bucketabstime --------------- 13954 (1 row)
- bucketbool (value, flag)
Description: Hashes the value in the bool format and finds the corresponding hash bucket.
Parameter: value indicates the value to be converted, which is of the bool type. flag is of the int type, indicating the data distribution mode. The value 0 indicates hash distribution.
Return type: int32
Example:
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openGauss=# select bucketbool(true,1); bucketbool ------------ 1 (1 row) openGauss=# select bucketbool(false,1); bucketbool ------------ 0 (1 row)
- bucketbpchar(value, flag)
Description: Hashes the value in the bpchar format and finds the corresponding hash bucket.
Parameter: value indicates the value to be converted, which is of the bpchar type. flag is of the int type, indicating the data distribution mode. The value 0 indicates hash distribution.
Return type: int32
Example:
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openGauss=# select bucketbpchar('test',1); bucketbpchar -------------- 9761 (1 row)
- bucketbytea (value, flag)
Description: Hashes the value in the bytea format and finds the corresponding hash bucket.
Parameter: value indicates the value to be converted, which is of the bytea type. flag is of the int type, indicating the data distribution mode. The value 0 indicates hash distribution.
Return type: int32
Example:
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openGauss=# select bucketbytea('test',1); bucketbytea ------------- 9761 (1 row)
- bucketcash (value, flag)
Description: Hashes the value in the money format and finds the corresponding hash bucket.
Parameter: value indicates the value to be converted, which is of the money type. flag is of the int type, indicating the data distribution mode. The value 0 indicates hash distribution.
Return type: int32
Example:
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openGauss=# select bucketcash(10::money,1); bucketcash ------------ 8468 (1 row)
- getbucket (value, flag)
Description: Obtains the hash bucket from the distribution column.
value indicates the value to be entered, which can be of the following types:
"char", abstime, bigint, boolean,bytea, character varying, character, date, double precision, int2vector, integer, interval, money, name, numeric, nvarchar2, oid, oidvector, raw, real, record, reltime, smalldatetime, smallint,text, time with time zone, time without time zone, timestamp with time zone, timestamp without time zone, tinyint, uuid
flag is of the int type, indicating the data distribution mode.
Return type: integer
Example:
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openGauss=# select getbucket(10,'H'); getbucket ----------- 14535 (1 row) openGauss=# select getbucket(11,'H'); getbucket ----------- 13449 (1 row) openGauss=# select getbucket(11,'R'); getbucket ----------- 13449 (1 row) openGauss=# select getbucket(12,'R'); getbucket ----------- 9412 (1 row)
- 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 anyrange 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 hash indexing on inet/cidr and 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)
- bucketchar
Description: Calculates the hash value of the input parameter.
Parameter: char, integer
Return type: integer
- bucketdate
Description: Calculates the hash value of the input parameter.
Parameter: date, integer
Return type: integer
- bucketfloat4
Description: Calculates the hash value of the input parameter.
Parameter: real, integer
Return type: integer
- bucketfloat8
Description: Calculates the hash value of the input parameter.
Parameters: double precision, integer
Return type: integer
- bucketint1
Description: Calculates the hash value of the input parameter.
Parameter: tinyint, integer
Return type: integer
- bucketint2
Description: Calculates the hash value of the input parameter.
Parameter: smallint, integer
Return type: integer
- bucketint2vector
Description: Calculates the hash value of the input parameter.
Parameter: int2vector, integer
Return type: integer
- bucketint4
Description: Calculates the hash value of the input parameter.
Parameter: integer, integer
Return type: integer
- bucketint8
Description: Calculates the hash value of the input parameter.
Parameter: bigint, integer
Return type: integer
- bucketinterval
Description: Calculates the hash value of the input parameter.
Parameter: interval, integer
Return type: integer
- bucketname
Description: Calculates the hash value of the input parameter.
Parameter: name, integer
Return type: integer
- bucketnumeric
Description: Calculates the hash value of the input parameter.
Parameter: numeric, integer
Return type: integer
- bucketnvarchar2
Description: Calculates the hash value of the input parameter.
Parameter: nvarchar2, integer
Return type: integer
- bucketoid
Description: Calculates the hash value of the input parameter.
Parameters: oid, integer
Return type: integer
- bucketoidvector
Description: Calculates the hash value of the input parameter.
Parameter: oidvector, integer
Return type: integer
- bucketraw
Description: Calculates the hash value of the input parameter.
Parameter: raw, integer
Return type: integer
- bucketreltime
Description: Calculates the hash value of the input parameter.
Parameter: reltime, integer
Return type: integer
- bucketsmalldatetime
Description: Calculates the hash value of the input parameter.
Parameter: smalldatetime, integer
Return type: integer
- buckettext
Description: Calculates the hash value of the input parameter.
Parameter: text, integer
Return type: integer
- buckettime
Description: Calculates the hash value of the input parameter.
Parameter: time without time zone, integer
Return type: integer
- buckettimestamp
Description: Calculates the hash value of the input parameter.
Parameter: timestamp without time zone, integer
Return type: integer
- buckettimestamptz
Description: Calculates the hash value of the input parameter.
Parameter: timestamp with time zone, integer
Return type: integer
- buckettimetz
Description: Calculates the hash value of the input parameter.
Parameter: time with time zone, integer
Return type: integer
- bucketuuid
Description: Calculates the hash value of the input parameter.
Parameter: uuid, integer
Return type: integer
- bucketvarchar
Description: Calculates the hash value of the input parameter.
Parameter: character varying, integer
Return type: integer
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