Re: chr() is still too loose about UTF8 code points

Noah Misch <noah@leadboat.com> writes:
> On Fri, May 16, 2014 at 11:05:08AM -0400, Tom Lane wrote:
>> I think this probably means we need to change chr() to reject code points
>> above 10ffff.  Should we back-patch that, or just do it in HEAD?

> The compatibility risks resemble those associated with the fixes for bug
> #9210, so I recommend HEAD only:

> http://www.postgresql.org/message-id/flat/20140220043940.GA3064539@tornado.leadboat.com

While I'd be willing to ignore that risk so far as code points above
10ffff go, if we want pg_utf8_islegal to be happy then we will also
have to reject surrogate-pair code points.  It's not beyond the realm
of possibility that somebody is intentionally generating such code
points with chr(), despite the dump/reload hazard.  So now I agree
that this is sounding more like a major-version-only behavioral change.
        regards, tom lane