PG Bug reporting form <noreply@postgresql.org> writes:
> create function f() returns text as $$
> declare
> s text;
> begin
> select b into s from t where a = 1;
> truncate t;
> return s;
> end;
> $$ language plpgsql;
> postgres=# select f();
> ERROR: missing chunk number 0 for toast value 24727 in pg_toast_24722
To prevent that, every fetch into a plpgsql variable would have
to immediately detoast the value, in case somebody did something
as weird as dropping/truncating the table later in the function.
That's an awfully expensive bit of protection. We do in fact
do it like that in procedures (more specifically, in non-atomic
contexts), so a possible workaround for you is to make this a
procedure not a function. I'm disinclined to change it otherwise.
regards, tom lane