Re: 7.0 release notes should call out incompatible changes more clearly

Andrew McMillan <Andrew@catalyst.net.nz> writes:
>> 2. SELECT DISTINCT ON syntax has changed --- now need parentheses
>> around the item being DISTINCT'ed.

> I have just upgraded my development machine today and this is proving to
> be a real pain in the neck as I seem to have used this all over the
> place :-)

> Can anyone suggest any syntax that I could use in the interim which will
> be compatible with 7.0 but which will also work with 6.5.3 so that I can
> minimise the pain of upgrading?

Er ... don't use DISTINCT ON?  It's not to be found anywhere in the
SQL92 specs, so if you want to run your app on a variety of DBMSes,
that's your only choice anyway.

If you are a heavy user of DISTINCT ON, I should think you'd gladly
accept a little conversion pain for the benefit of being able to do
DISTINCT ON multiple expressions, instead of only one unadorned
column name.
        regards, tom lane