Re: BUG #16805: "ALTER TABLE ... ADD COLUMN IF NOT EXISTS ... PRIMARY KEY" fails if column exists and is the primary

PG Bug reporting form <noreply@postgresql.org> writes:
> ALTER TABLE IF EXIST foo ADD COLUMN IF NOT EXISTS id BIGSERIAL PRIMARY KEY;
> Fails if "id" exists and is already the primary key.

Yeah, known problem.  This is fixed in v13, but the fix seemed too
invasive for a back-patch (see [1] and follow-on fixes).

            regards, tom lane

[1] https://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=1281a5c90