Re: Incorrect sort result caused by ROLLUP and WHERE operation

"=?utf-8?B?6LCt5b+g5rab?=" <zhongtao(dot)tan(at)seaboxdata(dot)com> writes:
> create table t1(a int, b int);
> insert into t1 values(1,1),(1,2);
> select a,b,sum(10) as s from t1 where a = 1 group by rollup(a,b) order by a, s desc;

Yeah. This is fixed in HEAD (v18-to-be) but the fix is too invasive
to consider back-patching. Basically the problem is that older
versions don't understand that the post-ROLLUP value of "a" can be
different from the pre-ROLLUP value, so they think the "where a = 1"
clause removes any need to sort by "a".

As a workaround you could write something like "order by a+0, s desc"
to fool the optimizer into considering the ordering column to be
different from the value that's constrained by WHERE.

regards, tom lane