Function not found while creating partial index

On Sun, 2026-02-01 at 13:56 -0500, Chris Hanks wrote:

Hello! The following series of statements results in an unexpected (to me) error on 18.0 and 18.1:

CREATE FUNCTION my_function_1(n integer) RETURNS integer AS 'SELECT n' LANGUAGE SQL IMMUTABLE;
CREATE FUNCTION my_function_2(n integer) RETURNS integer AS 'SELECT my_function_1(n)' LANGUAGE SQL IMMUTABLE;
CREATE SCHEMA my_schema;
CREATE TABLE my_schema.my_table (my_number integer);
CREATE INDEX my_index ON my_schema.my_table (my_number) WHERE my_function_2(my_number) = 4;

The CREATE INDEX fails with the following error:

ERROR:  function my_function_1(integer) does not exist
LINE 1: SELECT my_function_1(n)
               ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
QUERY:  SELECT my_function_1(n)
CONTEXT:  SQL function "my_function_2" during inlining

SQL state: 42883

If I change the definition of my_function_2 to 'SELECT public.my_function_1(n)' then the index builds successfully, so that's my current workaround.

That's not the workaround, that's the proper solution.

See the documentation (https://www.postgresql.org/docs/current/sql-createindex.html):

While CREATE INDEX is running, the search_path is temporarily changed to pg_catalog, pg_temp.

Yours,
Laurenz Albe