Re: COALESCE implementation question

At 23:28 5/08/00 -0400, Tom Lane wrote:
>Philip Warner <pjw@rhyme.com.au> writes:
>>> Well, the standard is perfectly clear, isn't it?  If V(1) has side
>>> effects then trying to optimize this into just one evaluation of V(1)
>>> will generate non-spec-compliant results.
>
>> At least with the new function manager, if I feel te need I can write a
>> 'CoalesceValues' function (at least for fixed numbers of parameters).
>
>Mmm ... not really.  You could detect nulls all right, but a function-
>based version of COALESCE would evaluate *all* its arguments exactly
>once, which is certainly wrong.

Good point. Although in the specific case (two args, one of them constant),
it's not an issue. I guess I'll just have to live with double-evaluation,
and a COALESCE than can return NULL. Grumble grumble...


----------------------------------------------------------------
Philip Warner                    |     __---_____
Albatross Consulting Pty. Ltd.   |----/       -  \
(A.C.N. 008 659 498)             |          /(@)   ______---_
Tel: (+61) 0500 83 82 81         |                 _________  \
Fax: (+61) 0500 83 82 82         |                 ___________ |
Http://www.rhyme.com.au          |                /           \|                                |    --________--
PGP key available upon request,  |  /
and from pgp5.ai.mit.edu:11371   |/