Tom Lane wrote:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > update pk set id = max(id) + 2;
>
> I'm fairly sure this query is illegal per spec. There are ancient
> discussions in the archives about whether aggregates in an UPDATE target
> list can have a consistent interpretation or not. We never found one,
> but never got around to disallowing it either. Maybe it's time. If you
> try it with something like sum() you don't get a crash, but you do get
> rather bizarre behavior.
Yeah, I agree we should disallow it. For the curious, the bizarre behavior
is
alvherre=# update pk set id = count(id) ;
ERROR: ctid is NULL
alvherre=# update pk set id = sum(id) ;
ERROR: ctid is NULL
Clearly not a very useful error message.
> Having said that, this may well expose a bug in the MAX-optimization
> code that has consequences for more useful queries. I'll take a look
> later today if no one beats me to it.
I refrain -- tried following it but I don't know that code at all.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
