Re: BUG #14059: BUG? function in select clause called more times when use offset

digoal(at)126(dot)com writes:
> postgres=# create or replace function f() returns void as $$
> declare
> begin
> raise notice 'called';
> end;
> $$ language plpgsql strict volatile;
> CREATE FUNCTION

> postgres=# select f(),* from ( values(1),(2),(3),(4),(5),(6) ) t(id) offset
> 3 limit 2;
> NOTICE: called
> NOTICE: called
> NOTICE: called
> NOTICE: called
> NOTICE: called
> f | id
> ---+----
> | 4
> | 5
> (2 rows)

> offset skip 3 tuple, but function f() called with 5 times, can we tuning
> this .
> or this is a bug?

No, it's not a bug. OFFSET only results in the skipped tuples not being
delivered to the client; it does not cause them not to be computed.

You could probably do something with a two-level select with the OFFSET
in the sub-select and the volatile function in the top level.

regards, tom lane