Re: Boolean casting in 7.3 -> changed?

On Wednesday 27 November 2002 06:23, Tom Lane wrote:
> Ian Barwick <barwick(at)gmx(dot)net> writes:
> > in 7.3 the following no longer works:
> > template1=> select 0::bool;
> > ERROR: Cannot cast type integer to boolean
>
> Note that both old and new versions reject
> select 0::int4::bool;
>
> I believe the behavioral change is a consequence of Rod Taylor's
> DOMAIN patch: it essentially eliminated the old parser_typecast_constant()
> routine in order to ensure that constraints associated with a domain
> would get applied in examples like "select 0::domaintypename".
>
> I wasn't totally happy with Rod's patch, for reasons that I couldn't put
> my finger on at the time, but perhaps my hindbrain understood that there
> would be noticeable behavioral changes. But be that as it may, the code
> is in there now and is unlikely to get reverted. There isn't any place
> in our docs that promises that you can coerce an integer-looking literal
> to bool --- and one could argue that allowing such is just opening the
> door for typos.

Thanks for the explanation. I'm not screaming for a reversion ;-), but
changing behaviour which was implicitly valid in previous
versions is bound to cause a few people a little head scratching
when converting applications to 7.3 (I'm sure I can't be the only one).

How about a line in HISTORY under "Migration to version 7.3" along
the lines of:

"Casting integers to boolean (for example, 0::bool) is no longer allowed,
use '0'::bool instead".

Ian Barwick
barwick(at)gmx(dot)net