Help Center/ GaussDB(DWS)/ SQL Syntax Reference (9.1.0.x)/ DDL Syntax/ ALTER FUNCTION
Updated on 2024-12-18 GMT+08:00
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ALTER FUNCTION

Function

ALTER FUNCTION modifies the attributes of a customized function.

Precautions

Only the owner of a function or a system administrator can run this statement. The user who wants to change the owner of a function must be a direct or indirect member of the newly owned role. If a function involves operations on temporary tables, the ALTER FUNCTION cannot be used.

Syntax

  • Modify the additional parameter of the customized function. 
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    ALTER FUNCTION function_name ( [ { [ argmode ] [ argname ] argtype} [, ...] ] )
    action [ ... ] [ RESTRICT ];

    The syntax of the action clause is as follows:

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    {CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT}
 | {IMMUTABLE | STABLE | VOLATILE}
 | {SHIPPABLE | NOT SHIPPABLE}
 | {NOT FENCED | FENCED}
 | {MASKED | NOT MASKED}
 | [ NOT ] LEAKPROOF
 | { [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER }
 | AUTHID { DEFINER | CURRENT_USER }
 | COST execution_cost
 | ROWS result_rows
 | SET configuration_parameter { { TO | = } { value | DEFAULT }| FROM CURRENT}
 | RESET {configuration_parameter | ALL}
  • Change the name of a user-defined function. The new function name can be prefixed with the name of the schema where the original function is located. The schema name cannot be changed at the same time. 
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    ALTER FUNCTION funname ( [ { [ argmode ] [ argname ] argtype} [, ...] ] )
    RENAME TO new_name;
ALTER FUNCTION funname ( [ { [ argmode ] [ argname ] argtype} [, ...] ] )
    RENAME TO schema.new_name;
  • Modify the owner of the customized function. 
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    ALTER FUNCTION funname ( [ { [ argmode ] [ argname ] argtype} [, ...] ] )
    OWNER TO new_owner;
  • Modify the schema of the customized function. 
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    ALTER FUNCTION funname ( [ { [ argmode ] [ argname ] argtype} [, ...] ] )
    SET SCHEMA new_schema;

Parameter Description

  • function_name

    Specifies the function name to be modified.

    Value range: An existing function name.

  • argmode

    Specifies whether a parameter is an input or output parameter.

    Value range: IN, OUT, IN OUT

  • argname

    Indicates the parameter name.

    Value range: A string. It must comply with the naming convention.

  • argtype

    Specifies the parameter type.

    Value range: A valid type. For details, see Data Types.

  • CALLED ON NULL INPUT

    Declares that some parameters of the function can be invoked in normal mode if the parameter values are NULL. By default, the usage is the same as specifying the parameters.

  • RETURNS NULL ON NULL INPUT

    STRICT

    Indicates that the function always returns NULL whenever any of its arguments are NULL. If this parameter is specified, the function is not executed when there are null parameters; instead a null result is assumed automatically.

    The usage of RETURNS NULL ON NULL INPUT is the same as that of STRICT.

  • IMMUTABLE

    Indicates that the function always returns the same result if the parameter values are the same.

  • STABLE

    Indicates that the function cannot modify the database, and that within a single table scan it will consistently return the same result for the same parameter values, but that its result varies by SQL statements.

  • VOLATILE

    Indicates that the function value can change in one table scanning and no optimization is performed.

  • SHIPPABLE

    NOT SHIPPABLE

    Indicates whether the function can be pushed down to DNs for execution.

    • Functions of the IMMUTABLE type can always be pushed down to the DNs.
    • Functions of the STABLE or VOLATILE type can be pushed down to DNs only if their attribute is SHIPPABLE.
  • MASKED | NOT MASKED

    Specifies whether the function performs masking when the guc parameter enable_redactcol_computable is enabled. MASKED supports system function modification and cannot be used together with actions in other ALTER functions.

  • LEAKPROOF

    Indicates that the function has no side effect and specifies that the parameter includes only the returned value. LEAKPROOF can be set only by the system administrator.

  • (Optional) EXTERNAL

    The objective is to be compatible with SQL. This feature applies to all functions, including external functions.

  • SECURITY INVOKER

    AUTHID CURREN_USER

    Declares that the function will be executed according to the permission of the user that invokes it. By default, the usage is the same as specifying the parameters.

    SECURITY INVOKER and AUTHID CURREN_USER have the same functions.

  • SECURITY DEFINER

    AUTHID DEFINER

    Specifies that the function is to be executed with the permissions of the user that created it.

    The usage of AUTHID DEFINER is the same as that of SECURITY DEFINER.

  • COST execution_cost

    A positive number giving the estimated execution cost for the function.

    The unit of execution_cost is cpu_operator_cost.

    Value range: A positive number.

  • ROWS result_rows

    Estimates the number of rows returned by the function. This is only allowed when the function is declared to return a set.

    Value range: A positive number. The default is 1000 rows.

  • configuration_parameter
    • value

      Sets a specified database session parameter to a specified value. If the value is DEFAULT or RESET, the default setting is used in the new session. OFF closes the setting.

      Value range: A string

      • DEFAULT
      • OFF
      • RESET

      Specifies the default value.

    • from current

      Uses the value of configuration_parameter of the current session.

  • new_name

    Specifies the new name of a function. To change a function's schema, you must also have the CREATE permission on the new schema.

    Value range: A string. It must comply with the naming convention.

  • new_owner

    Specifies the new owner of a function. To alter the owner, the new owner must also be a direct or indirect member of the new owning role, and that role must have CREATE permission on the function's schema.

    Value range: Existing user roles.

  • new_schema

    Specifies the new schema of a function.

    Value range: Existing schemas.

Examples

Alter the execution rule of function add to IMMUTABLE (that is, the same result is returned if the parameter remains unchanged):

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ALTER FUNCTION func_add_sql2(INTEGER, INTEGER) IMMUTABLE;

Change the name of the add function to add_two_number.

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ALTER FUNCTION func_add_sql2(INTEGER, INTEGER) RENAME TO add_two_number;

Change the name of the function add in tpcds to add_two_number, and prefix it with the original schema name.

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ALTER FUNCTION tpcds.func_add_sql2(INTEGER, INTEGER) RENAME TO tpcds.add_two_number;

Change the owner of function add to dbadmin:

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ALTER FUNCTION add_two_number(INTEGER, INTEGER) OWNER TO dbadmin;

Helpful Links

CREATE FUNCTION, DROP FUNCTION

Parent topic: DDL Syntax