ALTER_FUNCTION(7)

✨ ALTER FUNCTION ✨

okay bestie, welcome to ALTER FUNCTION from the PostgreSQL 18.6 docs, page ALTER FUNCTION(7) — yes that's the whole vibe, we're changing the definition of a function and we're gonna be so normal about it 💖

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🌸 NAME 🌸

ALTER_FUNCTION — change the definition of a function

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🎀 SYNOPSIS 🎀

ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    action [ ... ] [ RESTRICT ]
ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    RENAME TO new_name
ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    SET SCHEMA new_schema
ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    [ NO ] DEPENDS ON EXTENSION extension_name

where action is 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 }
    COST execution_cost
    ROWS result_rows
    SUPPORT support_function
    SET configuration_parameter { TO | = } { value | DEFAULT }
    SET configuration_parameter FROM CURRENT
    RESET configuration_parameter
    RESET ALL

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🦋 DESCRIPTION 🦋

ALTER FUNCTION changes the definition of a function. that's it, that's the whole girl 💅

now listen — you must own the function to use ALTER FUNCTION. and if you wanna change a function's schema, you also need CREATE privilege on the new schema. to alter the owner you have to be able to SET ROLE to the new owning role, and that role has to have CREATE privilege on the function's schema. (these restrictions are there to enforce that altering the owner doesn't let you do anything you couldn't already do by dropping and recreating the function. however, a superuser can alter ownership of any function anyway 👑 no cap.)

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💖 PARAMETERS 💖

• name — the name (optionally schema-qualified) of an existing function. if no argument list is specified, the name must be unique in its schema. otherwise it's giving ambiguous and Postgres will not be happy with you 😭
• argmode — the mode of an argument: IN, OUT, INOUT, or VARIADIC. if you omit it, the default is IN. heads up: 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. out args, we simply do not care about you 🙈
• argname — the name of an argument. and again, 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. names are just decoration here fr fr ✨
• argtype — the data type(s) of the function's arguments (optionally schema-qualified), if any.
• new_name — the new name of the function. rebrand era 🌈
• 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. yes that's a whole thing, keep it in mind 🫶
• new_schema — the new schema for the function.
• DEPENDS ON EXTENSION extension_name
• NO 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. bestie that's a lot of dropping 💀
• CALLED ON NULL INPUT
• RETURNS NULL ON NULL INPUT
• STRICT — CALLED 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 (CREATE_FUNCTION(7)) for more information.
• IMMUTABLE
• STABLE
• VOLATILE — change the volatility of the function to the specified setting. see CREATE FUNCTION (CREATE_FUNCTION(7)) for details. pick your fighter ✨
• [ 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 (CREATE_FUNCTION(7)) for more information about this capability.
• PARALLEL — change whether the function is deemed safe for parallelism. see CREATE FUNCTION (CREATE_FUNCTION(7)) for details. parallel girlies stay winning 🔥
• LEAKPROOF — change whether the function is considered leakproof or not. see CREATE FUNCTION (CREATE_FUNCTION(7)) for more information about this capability.
• COST execution_cost — change the estimated execution cost of the function. see CREATE FUNCTION (CREATE_FUNCTION(7)) for more information.
• ROWS result_rows — change the estimated number of rows returned by a set-returning function. see CREATE FUNCTION (CREATE_FUNCTION(7)) for more information.
• SUPPORT support_function — set or change the planner support function to use for this function. see Section 36.11 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. no removing, only replacing, we don't make the rules 💅

• configuration_parameter
• value — 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(7) and Chapter 19 for more information about allowed parameter names and values.

• RESTRICT — ignored for conformance with the SQL standard. it's just there for the vibe, bestie 🎀

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🌟 EXAMPLES 🌟

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. it's giving "I just work here" energy 🌸

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🌈 COMPATIBILITY 🌈

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
• change the owner, schema, or volatility of a function

the standard also requires the RESTRICT key word, which is optional in PostgreSQL. so we're the chill ones, obviously 💅

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💜 SEE ALSO 💜

CREATE FUNCTION (CREATE_FUNCTION(7)), DROP FUNCTION (DROP_FUNCTION(7)), ALTER PROCEDURE (ALTER_PROCEDURE(7)), ALTER ROUTINE (ALTER_ROUTINE(7))

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and that's the whole page bestie!! this was PostgreSQL 18.6, dated 2026, from ALTER FUNCTION(7) — go forth and alter responsibly, ily 🫶✨💖