ALTER FUNCTION — change the definition of a function
ALTER FUNCTIONname[ ( [ [argmode] [argname]argtype[, ...] ] ) ]action[ ... ] [ RESTRICT ] ALTER FUNCTIONname[ ( [ [argmode] [argname]argtype[, ...] ] ) ] RENAME TOnew_nameALTER FUNCTIONname[ ( [ [argmode] [argname]argtype[, ...] ] ) ] OWNER TO {new_owner| CURRENT_USER | SESSION_USER } ALTER FUNCTIONname[ ( [ [argmode] [argname]argtype[, ...] ] ) ] SET SCHEMAnew_schemaALTER FUNCTIONname[ ( [ [argmode] [argname]argtype[, ...] ] ) ] [ NO ] DEPENDS ON EXTENSIONextension_namewhereactionis one of: CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT IMMUTABLE | STABLE | VOLATILE [ NOT ] LEAKPROOF [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER PARALLEL { UNSAFE | RESTRICTED | SAFE } COSTexecution_costROWSresult_rowsSUPPORTsupport_functionSETconfiguration_parameter{ TO | = } {value| DEFAULT } SETconfiguration_parameterFROM CURRENT RESETconfiguration_parameterRESET ALL
   ALTER FUNCTION changes the definition of a
   function.
  
   You must own the function to use ALTER FUNCTION.
   To change a function's schema, you must also have CREATE
   privilege on the new schema.
   To alter the owner, you must also be a direct or indirect member of the new
   owning role, and that role must have CREATE privilege on
   the function's schema.  (These restrictions enforce that altering the owner
   doesn't do anything you couldn't do by dropping and recreating the function.
   However, a superuser can alter ownership of any function anyway.)
  
nameThe name (optionally schema-qualified) of an existing function. If no argument list is specified, the name must be unique in its schema.
argmode
      The mode of an argument: IN, OUT,
      INOUT, or VARIADIC.
      If omitted, the default is IN.
      Note that ALTER FUNCTION does not actually pay
      any attention to OUT arguments, since only the input
      arguments are needed to determine the function's identity.
      So it is sufficient to list the IN, INOUT,
      and VARIADIC arguments.
     
argname
      The name of an argument.
      Note that ALTER FUNCTION does not actually pay
      any attention to argument names, since only the argument data
      types are needed to determine the function's identity.
     
argtypeThe data type(s) of the function's arguments (optionally schema-qualified), if any.
new_nameThe new name of the function.
new_owner
      The new owner of the function.  Note that if the function is
      marked SECURITY DEFINER, it will subsequently
      execute as the new owner.
     
new_schemaThe new schema for the function.
DEPENDS ON EXTENSION extension_nameNO DEPENDS ON EXTENSION extension_name
      This form marks the function as dependent on the extension, or no longer
      dependent on that extension if NO is specified.
      A function that's marked as dependent on an extension is dropped when the
      extension is dropped, even if CASCADE is not specified.
      A function can depend upon multiple extensions, and will be dropped when
      any one of those extensions is dropped.
     
CALLED ON NULL INPUTRETURNS NULL ON NULL INPUTSTRICTCALLED ON NULL INPUT changes the function so
       that it will be invoked when some or all of its arguments are
       null. RETURNS NULL ON NULL INPUT or
       STRICT changes the function so that it is not
       invoked if any of its arguments are null; instead, a null result
       is assumed automatically.  See CREATE FUNCTION
       for more information.
      
IMMUTABLESTABLEVOLATILEChange the volatility of the function to the specified setting. See CREATE FUNCTION for details.
[ EXTERNAL ] SECURITY INVOKER[ EXTERNAL ] SECURITY DEFINER
      Change whether the function is a security definer or not. The
      key word EXTERNAL is ignored for SQL
      conformance. See CREATE FUNCTION for more information about
      this capability.
     
PARALLELChange whether the function is deemed safe for parallelism. See CREATE FUNCTION for details.
LEAKPROOFChange whether the function is considered leakproof or not. See CREATE FUNCTION for more information about this capability.
COST execution_costChange the estimated execution cost of the function. See CREATE FUNCTION for more information.
ROWS result_rowsChange the estimated number of rows returned by a set-returning function. See CREATE FUNCTION for more information.
SUPPORT support_functionSet or change the planner support function to use for this function. See Section 37.11 for details. You must be superuser to use this option.
      This option cannot be used to remove the support function altogether,
      since it must name a new support function.  Use CREATE OR
      REPLACE FUNCTION if you need to do that.
     
configuration_parametervalue
        Add or change the assignment to be made to a configuration parameter
        when the function is called.  If
        value is DEFAULT
        or, equivalently, RESET is used, the function-local
        setting is removed, so that the function executes with the value
        present in its environment.  Use RESET
        ALL to clear all function-local settings.
        SET FROM CURRENT saves the value of the parameter that
        is current when ALTER FUNCTION is executed as the value
        to be applied when the function is entered.
       
See SET and Chapter 19 for more information about allowed parameter names and values.
RESTRICTIgnored for conformance with the SQL standard.
   To rename the function sqrt for type
   integer to square_root:
ALTER FUNCTION sqrt(integer) RENAME TO square_root;
   To change the owner of the function sqrt for type
   integer to joe:
ALTER FUNCTION sqrt(integer) OWNER TO joe;
   To change the schema of the function sqrt for type
   integer to maths:
ALTER FUNCTION sqrt(integer) SET SCHEMA maths;
   To mark the function sqrt for type
   integer as being dependent on the extension
   mathlib:
ALTER FUNCTION sqrt(integer) DEPENDS ON EXTENSION mathlib;
To adjust the search path that is automatically set for a function:
ALTER FUNCTION check_password(text) SET search_path = admin, pg_temp;
   To disable automatic setting of search_path for a function:
ALTER FUNCTION check_password(text) RESET search_path;
The function will now execute with whatever search path is used by its caller.
   This statement is partially compatible with the ALTER
   FUNCTION statement in the SQL standard. The standard allows more
   properties of a function to be modified, but does not provide the
   ability to rename a function, make a function a security definer,
   attach configuration parameter values to a function,
   or change the owner, schema, or volatility of a function. The standard also
   requires the RESTRICT key word, which is optional in
   PostgreSQL.