On Thu, 23 Jun 2005, Tom Lane wrote:
> Pavel Stehule <stehule@kix.fsv.cvut.cz> writes:
> + /* If any argument is null, then result is null (for GREATEST and LEAST)*/
>
> Are you sure about that? The only reference I could find says that
> these functions are not strict in Oracle:
>
> http://download-east.oracle.com/otn_hosted_doc/rdb/pdf/sql_ref_v71_vol1.pdf
> on page 2-185:
>
> The NULL keyword can appear in the list but is ignored. However, not all
> value expressions can be specified as NULL. That is, a non-NULL value
> expression must be in the list so that the data type for the expression
> can be determined.
> The GREATEST and LEAST functions can result in NULL only if at run time
> all value expressions result in NULL.
>
> The strict interpretation is mathematically cleaner, no doubt, but
> offhand it seems less useful.
>
I know it, But when moustly PostgreSQL function is strict I desided so
greatest and least will be strict. There is two analogy:
one, normal comparing which implicate strinct
aggregate function which ignore NULL.
what I have to chose? For compatibility there isn't biggeer changes. Only
//if (*isNull)
// return value;
if (result && *isNull == false)
{
locfcinfo.arg[0] = result;
...
}
-----
foreach(arg, ..)
{
if (IsA(e, Const))
if (!((Const *) e)->constisnull)
newargs = lappend(newargs, e);
}
if (newargs == NULL)
return (Node *) makeNullConst(varargexpr->..);
-----
Tom I don't know, what is better. Maybe Oracle,
because
least(nullif(col2, +max), nullif(col2, +max)) isn't really readable, but
it's "precedens" for PostgreSQL. I selected more conservative solution,
but my patches are only start points for discussion (really) :).
Please, if You think, so Oracle way is good, correct it.
Best regards
Pavel
