On Mon, Jul 21, 2008 at 08:19:35AM +0900, Tatsuo Ishii wrote:
> > > Thus I think we should avoid this kind of ORDER BY. Probably we should
> > > avoid LIMIT/OFFSET and FOR UPDATE as well.
> >
> > What of index-optimized SELECT max(...) ?
>
> Aggregate functions in a recursive term is prohibited by the
> standard. For example,
>
> WITH RECURSIVE x(n) AS (SELECT 1 UNION ALL SELECT max(n) FROM x)
> SELECT * FROM x;
>
> produces an error.

On the other side of UNION ALL, it's OK, right? For example,

WITH RECURSIVE x(n) AS (
SELECT max(i) FROM t
UNION ALL
SELECT n+1 FROM x WHERE n < 20
)

Cheers,
David.
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> On Mon, Jul 21, 2008 at 08:19:35AM +0900, Tatsuo Ishii wrote:
> > > > Thus I think we should avoid this kind of ORDER BY. Probably we should
> > > > avoid LIMIT/OFFSET and FOR UPDATE as well.
> > >
> > > What of index-optimized SELECT max(...) ?
> >
> > Aggregate functions in a recursive term is prohibited by the
> > standard. For example,
> >
> > WITH RECURSIVE x(n) AS (SELECT 1 UNION ALL SELECT max(n) FROM x)
> > SELECT * FROM x;
> >
> > produces an error.
>
> On the other side of UNION ALL, it's OK, right? For example,
>
> WITH RECURSIVE x(n) AS (
> SELECT max(i) FROM t
> UNION ALL
> SELECT n+1 FROM x WHERE n < 20
> )

Yes, aggregate functions in the non-recursive term is allowed by the
standard.
--
Tatsuo Ishii
SRA OSS, Inc. Japan

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