Re: Statistical aggregate functions are not working with PARTIAL aggregation

At Tue, 07 May 2019 20:47:28 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote in <20190507.204728.233299873.horiguchi.kyotaro@lab.ntt.co.jp>
> Hello.
> 
> At Tue, 7 May 2019 14:39:55 +0530, Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com> wrote in <CAKcux6=YBMCntcafSs_22dS1ab6mGay_QUaHx-nvg+_FVPMg3Q@mail.gmail.com>
> > Hi,
> > As this issue is reproducible without partition-wise aggregate also,
> > changing email subject from "Statistical aggregate functions are not
> > working with partitionwise aggregate " to "Statistical aggregate functions
> > are not working with PARTIAL aggregation".
> > 
> > original reported test case and discussion can be found at below link.
> > https://www.postgresql.org/message-id/flat/CAKcux6%3DuZEyWyLw0N7HtR9OBc-sWEFeByEZC7t-KDf15FKxVew%40mail.gmail.com
> 
> The immediate reason for the behavior seems that
> EEOP_AGG_STRICT_INPUT_CHECK_ARGS considers non existent second
> argument as null, which is out of arguments list in
> trans_fcinfo->args[].
> 
> The invalid deserialfn_oid case in ExecBuildAggTrans, it
> initializes args[1] using the second argument of the functoin
> (int8pl() in the case) so the correct numTransInputs here is 1,
> not 2.
> 
> I don't understand this fully but at least the attached patch
> makes the test case work correctly and this seems to be the only
> case of this issue.

This behavior is introduced by 69c3936a14 (in v11).  At that time
FunctionCallInfoData is pallioc0'ed and has fixed length members
arg[6] and argnull[7]. So nulls[1] is always false even if nargs
= 1 so the issue had not been revealed.

After introducing a9c35cf85c (in v12) the same check is done on
FunctionCallInfoData that has NullableDatum args[] of required
number of elements. In that case args[1] is out of palloc'ed
memory so this issue has been revealed.

In a second look, I seems to me that the right thing to do here
is setting numInputs instaed of numArguments to numTransInputs in
combining step.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center