Re: BUG #17088: FailedAssertion in prepagg.c

On Thu, Jul 8, 2021 at 2:14 PM Richard Guo <guofenglinux@gmail.com> wrote:

>
> On Thu, Jul 8, 2021 at 1:44 PM Richard Guo <guofenglinux@gmail.com> wrote:
>
>>
>> I think the culprit is that when replacing correlation uplevel vars with
>> Params, we do not handle the SubLinks in the arguments of uplevel
>> GroupingFunc. We expect build_subplan should take care of it. But in
>> build_subplan, we ignore GroupingFunc incorrectly.
>>
>> diff --git a/src/backend/optimizer/plan/subselect.c
>> b/src/backend/optimizer/plan/subselect.c
>> index 0881a208ac..e4918f275e 100644
>> --- a/src/backend/optimizer/plan/subselect.c
>> +++ b/src/backend/optimizer/plan/subselect.c
>> @@ -364,7 +364,8 @@ build_subplan(PlannerInfo *root, Plan *plan,
>> PlannerInfo *subroot,
>>                  * SS_replace_correlation_vars).  Do that now.
>>                  */
>>                 if (IsA(arg, PlaceHolderVar) ||
>> -                       IsA(arg, Aggref))
>> +                       IsA(arg, Aggref) ||
>> +                       IsA(arg, GroupingFunc))
>>                         arg = SS_process_sublinks(root, arg, false);
>>
>>
>
> I think we also need to change SS_process_sublinks to avoid recursing
> into the arguments of an outer GroupingFunc. And that leads to a fix as
> attached.
>

Update the patch with comments and test cases.

Thanks
Richard