"Peter J. Holzer" <hjp-pgsql(at)hjp(dot)at> writes:
> I noticed that an update was taking a long time and found this:
> [ crappy plan for join on IS NOT DISTINCT ]
Yeah, there's no optimization smarts at all for IS [NOT] DISTINCT.
It can't be converted into a merge qual, nor a hash qual, nor an
indexscan qual.
In principle this could be improved, but given how much work it'd be
and how seldom anyone complains, it's not likely to happen anytime soon.
regards, tom lane