Re: PL/pgSQL PERFORM with CTE

2013/8/20 David E. Wheeler <david(at)justatheory(dot)com>

> On Aug 20, 2013, at 2:31 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
>
> > but it works
> >
> > postgres=# do $$begin with x as (select 10) insert into omega select *
> from x; end;$$;
> > DO
>
> But this does not:
>
> david=# DO $$
> david$# BEGIN
> david$# PERFORM * FROM (
> david$# WITH inserted AS (
> david$# INSERT INTO foo values (1) RETURNING id
> david$# ) SELECT inserted.id
> david$# ) x;
> david$# END;
> david$# $$;
> ERROR: WITH clause containing a data-modifying statement must be at the
> top level
> LINE 2: WITH inserted AS (
> ^
> QUERY: SELECT * FROM (
> WITH inserted AS (
> INSERT INTO foo values (1) RETURNING id
> ) SELECT inserted.id
> ) x
> CONTEXT: PL/pgSQL function inline_code_block line 3 at PERFORM
>
> yes, in this context you should not use a PERFORM

PL/pgSQL protect you before useless queries - so you can use a CTE without
returned result directly or CTE with result via PERFORM statement (and in
this case it must be unmodifing CTE).

Sorry, I don't see any problem - why you return some from CTE and then you
throw this result?

> Best,
>
> David
>
>