Re: BUG #4085: No implicit cast after coalesce

[Jeff Dwyer <jdwyer(at)patientslikeme(dot)com>]

OK, worksforme. I guess I still find it odd, but I much prefer  
explicitness & robustness to small values of 'work'.

Thanks for the prompt response.

-Jeff

On Apr 2, 2008, at 7:15 PM, Tom Lane wrote:

> Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> > Jeff Dwyer wrote:
> > > This seems like a bug to me. Why should an explicit cast be  
> > > necessary after
> > > a coalesce?
>
> > Because coalesce(null, '1900-1-2') has no other type information  
> > attached, so
> > it would have picked text by default as result type, and that then  
> > clashes
> > with the result type of coalesce(null,current_date), which can be  
> > derived to
> > be date.  This is a robustness improvement: 8.2 and earlier would  
> > silently
> > accept coalesce(null, 'abc') and apply text-semantics comparison.
>
> Yes.  The query "worked" in pre-8.3 only for rather small values of
> "work": if you had been using a non-ISO datestyle the comparisons  
> would
> in fact have come out wrong.  Also, it being a textual rather than  
> date
> comparison, any index on the date column being compared to wouldn't  
> have
> been used.
>
> 			regards, tom lane