Default Arguments
| Arguments | Result |
|---|---|
| None | HASHAMP () returns an INTEGER that is one less than the maximum number of AMPs in the system. |
| expression is not specified | For a contiguous map: The function returns an INTEGER representing the highest AMP number in the specified or default contiguous map. For a contiguous map starting at AMP zero, adding one to the result gives the total number of AMPs in the contiguous map. For a sparse map: Expression must be specified for a sparse map. |
| expression is specified | The function returns the ID of the primary AMP corresponding to the hash bucket number specified in expression, based on the specified or default map. |
Default Map
To determine the default map, the system evaluates the following, in order, and uses the first map found:
- User profile.
- User.
- System.
Expression
The expression argument must evaluate to an INTEGER data type where the range of valid values depends on the system hash bucket size.
| IF the hash bucket size is … | THEN the range of values for expression is … |
|---|---|
| 16 bits | 0 to 65,535. |
| 20 bits | 0 to 1,048,575. |
For information on how to set the system hash bucket size, see “DBS Control utility” in Teradata Vantage™ - Database Utilities, B035-1102.
If expression cannot be implicitly converted to an INTEGER, an error is reported.
- Numeric
- Character
- DATE
To define an implicit cast for a UDT, use the CREATE CAST statement and specify the AS ASSIGNMENT clause. For more information, see Teradata Vantage™ - SQL Data Definition Language Syntax and Examples, B035-1144.
Implicit type conversion of UDTs for system operators and functions, including HASHAMP, is a Teradata extension to the ANSI SQL standard. To disable this extension, set the DisableUDTImplCastForSysFuncOp field of the DBS Control Record to TRUE.