Postgres 14

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Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.

create table users(
    id int primary key,
    name text);
    
insert into users values
(1, 'John');

CREATE TABLE



INSERT 0 1


create or replace function protect_users_id()
returns trigger language plpgsql as $$
begin
    if old.id <> new.id then
        raise exception 'Cannot change users.id';
    end if;
end $$;

create trigger protect_users_id
before update on users
for each row execute procedure protect_users_id();

CREATE FUNCTION



CREATE TRIGGER


update users set
    id = 2
where id = 1;

ERROR:  Cannot change users.id
CONTEXT:  PL/pgSQL function protect_users_id() line 4 at RAISE