Re: [PATCHES] Function's LEAST, GREATEST and DECODE (Oracle vararg polymorphic functions)

[ moving to -hackers for a wider audience ]

Today's issue: should the GREATEST/LEAST functions be strict (return
null if any input is null) or not (return null only if all inputs are
null, else return the largest/smallest of the non-null inputs)?

Pavel Stehule <stehule@kix.fsv.cvut.cz> writes:
> 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.

> 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.

I'm still favoring non-strict but it deserves more than two votes.
Anybody else have an opinion?
        regards, tom lane