Re: [HACKERS] having bug report

José Soares <jose@sferacarta.com> writes:
> * subqueries containing HAVING return incorrect results
> select istat from comuni where istat in (
> select istat from comuni group by istat having count(istat) > 1
> );
> ERROR:  rewrite: aggregate column of view must be at rigth side in qual
> select istat from comuni where istat in (
> select istat from comuni group by istat having 1 < count(istat)
> );
> ERROR:  pull_var_clause: Cannot handle node type 108

These are both known problems (at least, I had both in my todo list).

The first one appears to be a rewriter bug --- it seems to want to
implement count(istat) as a second nested sublink, and then it falls
over because it doesn't handle "subselect op something" as opposed to
"something op subselect".  But pushing count(istat) into a subselect
is not merely inefficient, it's *wrong* in this case because then the
group by won't affect it.

The second one is a problem in the planner/optimizer; it falls over on
sublinks in HAVING clauses (of course, this particular example wouldn't
trigger the problem were it not for the upstream rewriter bug, but it's
still a planner bug).  I think union_planner's handling of sublinks
needs considerable work, but was putting it off till after 6.5.

I will work on the second problem; I think the first one is in Jan's
turf...
        regards, tom lane