ALTER_FUNCTION(7pg17)

📦 version 17.11, in opensuse-leap 16.0

💅 ALTER FUNCTION — change the definition of a function

okay bestie, so you've got a function in your PostgreSQL 17.11 docs era and it's not serving what you need anymore? relatable. ALTER FUNCTION is your glow-up tool ✨ — it tweaks a function's definition without you having to drop it and rebuild it from scratch. icon behaviour, honestly.

🌸 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

look at all those choices. main character menu energy fr fr 🎀

🦋 DESCRIPTION 🦋

ALTER FUNCTION changes the definition of a function. that's it, that's the whole vibe check.

now the rules, and bestie you gotta listen to these 👇

  • 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 be able to SET ROLE to the new owning role, and that role must have CREATE privilege on the function's schema.
why so strict? because these restrictions enforce that altering the owner doesn't do anything you couldn't already do by dropping and recreating the function 🙈 makes sense honestly.

however — plot twist — a superuser can alter ownership of any function anyway. crown emoji 👑 no cap.

💖 PARAMETERS 💖

  • name — the name of an existing function, optionally schema-qualified. if you don't specify an argument list, the name has to be unique in its schema. no duplicates, we don't do that here 💅
  • argmode — the mode of an argument, and it's one of: IN, OUT, INOUT, or VARIADIC. if you omit it, the default is IN. heads up tho: ALTER FUNCTION does not actually pay any attention to OUT arguments, because only the input arguments are needed to figure out the function's identity. so it's totally sufficient to list the IN, INOUT, and VARIADIC arguments 🫶
  • argname — the name of an argument. and ngl, ALTER FUNCTION does not actually pay any attention to argument names either, since only the argument data types are needed to determine the function's identity. the types do all the talking ✨
  • 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. lowkey important: if the function is marked SECURITY DEFINER, it will subsequently execute as the new owner. so like, choose wisely bestie 😭
  • 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 marked as dependent on an extension is dropped when the extension is dropped, even if CASCADE is not specified. and a function can depend upon multiple extensions — it will be dropped when any one of those extensions is dropped. so many endings 💀
  • 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 info 🧚
  • IMMUTABLE, STABLE, VOLATILE — change the volatility of the function to the specified setting. see CREATE FUNCTION (CREATE_FUNCTION(7)) for details. pick your vibe 🔥
  • [ 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 info about this capability.
  • PARALLEL — change whether the function is deemed safe for parallelism. options are UNSAFE, RESTRICTED, or SAFE (that's the { UNSAFE | RESTRICTED | SAFE } up in the synopsis). see CREATE FUNCTION (CREATE_FUNCTION(7)) for details ⭐
  • LEAKPROOF — change whether the function is considered leakproof or not. see CREATE FUNCTION (CREATE_FUNCTION(7)) for more info about this capability.
  • COST execution_cost — change the estimated execution cost of the function. see CREATE FUNCTION (CREATE_FUNCTION(7)) for more info.
  • ROWS result_rows — change the estimated number of rows returned by a set-returning function. see CREATE FUNCTION (CREATE_FUNCTION(7)) for more info 🍓
  • 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. noted, bestie 📝
  • 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, purely for conformance with the SQL standard. it's literally just there to be polite 🙈

✨ EXAMPLES ✨

bestie these are the fun part, let's go 💅

rename the function sqrt for type integer to square_root:

ALTER FUNCTION sqrt(integer) RENAME TO square_root;

change the owner of the function sqrt for type integer to joe:

ALTER FUNCTION sqrt(integer) OWNER TO joe;

change the schema of the function sqrt for type integer to maths:

ALTER FUNCTION sqrt(integer) SET SCHEMA maths;

mark the function sqrt for type integer as being dependent on the extension mathlib:

ALTER FUNCTION sqrt(integer) DEPENDS ON EXTENSION mathlib;

adjust the search path that is automatically set for a function:

ALTER FUNCTION check_password(text) SET search_path = admin, pg_temp;

disable automatic setting of search_path for a function:

ALTER FUNCTION check_password(text) RESET search_path;

and after that last one, the function will now execute with whatever search path is used by its caller 🌀 iconic.

🌸 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

also, the standard requires the RESTRICT key word, which is optional in PostgreSQL. so we're out here being flexible 💁‍♀️

🎀 SEE ALSO 🎀

okay that's the whole page, you're basically a function-altering expert now 👑 go forth and ALTER responsibly, bestie 🫶

mwah 💋 — this has been PostgreSQL 17.11 documentation, dated 2026, signing off~

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