Help Center/ GaussDB/ Developer Guide(Centralized_V2.0-2.x)/ SQL Reference/ SQL Syntax/ ALTER FUNCTION
Updated on 2025-07-22 GMT+08:00
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ALTER FUNCTION

Description

Alters the attributes of a custom function.

Precautions

Only the function owner or a user granted the ALTER permission can run the ALTER FUNCTION command. System administrators have this permission by default. The following are permission restrictions depending on attributes to be modified:
  • If a function involves operations on temporary tables, ALTER FUNCTION cannot be used.
  • To modify the owner or schema of a function, you must be a function owner or system administrator and a member of the new owner role.
  • Only system administrators and the initial user can change the schema of a function to public.

Syntax

  • Modify the additional parameters of the user-defined function. 
    ALTER FUNCTION function_name ( [ { [ argname ] [ argmode ] argtype} [, ...] ] )
    action [ ... ] [ RESTRICT ];

    The syntax of the ACTION clause is as follows:

    {CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT}
 | {IMMUTABLE | STABLE | VOLATILE}
 | {SHIPPABLE | NOT SHIPPABLE}
 | {NOT FENCED | FENCED}
 | [ 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}
  • Rename the user-defined function. 
    ALTER FUNCTION function_name ( [ { [ argname ] [ argmode ] argtype} [, ...] ] )
    RENAME TO new_name;
  • Change the owner of the user-defined function. 
    ALTER FUNCTION function_name ( [ { [ argname ] [ argmode ] argtype} [, ...] ] )
    OWNER TO new_owner;
  • Modify the schema of the user-defined function. 
    ALTER FUNCTION function_name ( [ { [ argname ] [ argmode ] argtype} [, ...] ] )
    SET SCHEMA new_schema;

Parameters

  • function_name

    Specifies the name of the function to be modified.

    Value range: an existing function name.

  • argmode

    Specifies whether a parameter is an input or output parameter.

    Value range:

    • IN: declares input parameters.
    • OUT: declares output parameters.
    • INOUT: declares input and output parameters.
    • VARIADIC: declares parameters of the array type.
  • argname

    Specifies the parameter name.

    Value range: a string that complies with the Identifier Naming Conventions.

  • argtype

    Specifies the parameter type of the function.

  • CALLED ON NULL INPUT

    Declares that some parameters of the function can be called in normal mode if the parameter values are NULL. Omitting this parameter is the same as specifying it.

  • RETURNS NULL ON NULL INPUT

    STRICT

    Specifies that a function always returns NULL when the value of any of its parameters is NULL. If this parameter is specified, the function is not executed when there is NULL parameter; instead a NULL result is assumed automatically.

    RETURNS NULL ON NULL INPUT and STRICT have the same functions.

  • IMMUTABLE

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

  • STABLE

    Specifies 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 value, but its result varies by SQL statements.

  • VOLATILE

    Specifies that the function value can change in a single table scan and no optimization is performed.

  • LEAKPROOF

    Specifies that the function has no side effect and the parameter contains only the return value. LEAKPROOF can be set only by system administrators.

  • EXTERNAL

    (Optional) The purpose is to be compatible with SQL. This feature applies to all functions, not only external functions.

  • SECURITY INVOKER

    AUTHID CURRENT_USER

    Specifies that the function will be executed with the permissions of the user who calls it. Omitting this parameter is the same as specifying it.

    SECURITY INVOKER and AUTHID CURRENT_USER have the same functions.

  • SECURITY DEFINER

    AUTHID DEFINER

    Specifies that the function will be executed with the permissions of the user who created it.

    AUTHID DEFINER and SECURITY DEFINER have the same functions.

  • COST execution_cost

    Estimates the execution cost of a function.

    The unit of execution_cost is cpu_operator_cost.

    Value range: a positive integer.

  • 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 value is 1000.

  • 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 disables the setting.

      Value range: a string.

      • DEFAULT
      • OFF
      • RESET
      • Specified 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 the schema of a function, you must have the CREATE permission on the new schema.

    Value range: a string that complies with the Identifier Naming Conventions.

  • new_owner

    Specifies the new owner of a function. To change the owner of a function, the new owner must have the CREATE permission on the schema to which the function belongs.

    Value range: an existing user role.

  • new_schema

    Specifies the new schema of a function.

    Value range: an existing schema.

Examples

See Examples in "CREATE FUNCTION."

Helpful Links

CREATE FUNCTION and DROP FUNCTION

Parent topic: SQL Syntax