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:

  MogDB=# 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:

  MogDB=# select bucketbool(true,1);
   bucketbool
  ------------
            1
  (1 row)
  MogDB=#  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:

  MogDB=# 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:

  MogDB=# 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:

  MogDB=# 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, nvarchar, 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, and uuid

  flag is of the int type, indicating the data distribution mode.

  Return type: integer

  Example:

  MogDB=# select getbucket(10,'H');
   getbucket
  -----------
       14535
  (1 row)
  
  MogDB=# select getbucket(11,'H');
   getbucket
  -----------
       13449
  (1 row)
  
  MogDB=# select getbucket(11,'R');
   getbucket
  -----------
       13449
  (1 row)
  
  MogDB=# 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 anyarray type

  Return type: integer

  Example:

  MogDB=# 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.

  Parameter: key indicates the value of each column in the Group Clause.

  Return type: 32-bit hash value

  Example:

  Perform the following steps in sequence.
  MogDB=# 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
  MogDB=# select * from tt;
   a | b | c | d
  ---+---+---+---
  (0 rows)
  
  MogDB=# insert into tt values(1,2,3,4);
  INSERT 0 1
  MogDB=# select * from tt;
   a | b | c | d
  ---+---+---+---
   1 | 2 | 3 | 4
  (1 row)
  
  MogDB=# insert into tt values(5,6,7,8);
  INSERT 0 1
  MogDB=# select * from tt;
   a | b | c | d
  ---+---+---+---
   1 | 2 | 3 | 4
   5 | 6 | 7 | 8
  (2 rows)
  
  MogDB=# 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:

  MogDB=# 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:

  MogDB=# 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:

  MogDB=# 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:

  MogDB=# select hashbpchar('hello');
   hashbpchar
  -------------
   -1870292951
  (1 row)
  
  MogDB=# 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:

  MogDB=# CREATE TYPE b1 AS ENUM('good', 'bad', 'ugly');
  CREATE TYPE
  MogDB=# 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:

  MogDB=# 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:

  MogDB=# 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:

  MogDB=# 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:

  MogDB=# 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:

  MogDB=# select hashint2(20000);
    hashint2
  ------------
   -863179081
  (1 row)

• bucketchar

  Description: Calculates the hash value of the input parameter.

  Parameter: char and integer

  Return type: integer

• bucketdate

  Description: Calculates the hash value of the input parameter.

  Parameters: date and integer

  Return type: integer

• bucketfloat4

  Description: Calculates the hash value of the input parameter.

  Parameter: real and integer

  Return type: integer

• bucketfloat8

  Description: Calculates the hash value of the input parameter.

  Parameters: double precision and integer

  Return type: integer

• bucketint1

  Description: Calculates the hash value of the input parameter.

  Parameter: tinyint and integer

  Return type: integer

• bucketint2

  Description: Calculates the hash value of the input parameter.

  Parameters: smallint and integer

  Return type: integer

• bucketint2vector

  Description: Calculates the hash value of the input parameter.

  Parameter: int2vector and 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: nvarchar, 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.

  Parameters: uuid, integer

  Return type: integer

• bucketvarchar

  Description: Calculates the hash value of the input parameter.

  Parameter: character varying, integer

  Return type: integer