Re: BUG #16368: Incorrect function inlining in the presence of awindow function

The following bug has been logged on the website:

Bug reference:      16368
Logged by:          Elvis Pranskevichus
Email address:      elprans@gmail.com
PostgreSQL version: 12.2
Operating system:   Gentoo Linux
Description:       

Consider the following function:

CREATE OR REPLACE FUNCTION intfmt(input text, fmt text)
[...]
SELECT
  CASE WHEN fmt IS NULL
    THEN input::bigint
    ELSE to_number(input, fmt)::bigint
  END;
[...]
SELECT
[...] 

    intfmt('123,456', q.fmt) AS "out"

The expected result is the integer 123456, but the query fails with:

ERROR:  invalid input syntax for type bigint: "123,456"
CONTEXT:  SQL function "intfmt" during inlining

Which means that somehow during inlining of "intfmt" Postgres incorrectly
takes the first branch in the `CASE` expression.

This only happens in the
presence of the "first_value" window call in the nested query.