On Jul 17, 2012, at 2:32, Rafal Pietrak <rafal@xxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 2012-07-16 at 14:08 -0400, David Johnston wrote:
> [------------]
>>
>> Specific, but unknown (e.g., day of week, month, year, etc...) results could
>> return "NaN" though "NULL" is also, probably more, reasonable given the
>> context.
>>
>> The goal would be to use "Infinity" in case where "<>" comparisons are
>> common and use "NULL" where "=" comparisons are common.
>
> Is that even possible to implement? (e.g.: "SELECT * FROM log WHERE
> start_date <> 'XXXX-YY-ZZ' and end_date = 'ZZZZ-AA-BB'" - when both
> start_date and end_date possibly have 'infinity')
I was unclear. I intended "<>" to mean "greater than and less than comparisons" as opposed to not equals comparisons. Equality and inequality are two sides to the same coin.
>
> Anyway, "NaN" looks quite appealing, particulary since currently:
>
> SELECT date_part('year','infinity'::timestamp ) ;
> date_part
> -----------
> 0
> (1 row)
>
> ... can lead to applications misbehaving in strange ways.
>
> I feal that date_part() on infinity, should behave "similarly to"
> division by zero - an exception. But seeing a lot of code obfuscated
> with checks for division by zero before doing an opperation, I'd opt for
> silently returning a NaN in most cases, with fields like 'year',
> 'century', 'epoch', etc. returning 'Infinity'.
>
> -R
>
>
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