Re: array_agg(DISTINCT) caused a segmentation fault

On Mon, 13 Feb 2023 at 18:29, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
> =# SELECT array_agg(distinct val) FROM (SELECT NULL AS val FROM generate_series(1, 2)) hoge;
> LOG: server process (PID 76507) was terminated by signal 11: Segmentation fault: 11
> DETAIL: Failed process was running: SELECT array_agg(distinct val) FROM (SELECT NULL AS val FROM generate_series(1, 2)) hoge;

This was a fairly trivial logic bug in
ExecEvalPreOrderedDistinctSingle(). The JIT code calls that same
function and ExecEvalPreOrderedDistinctMulti() uses the standard
expression evaluation logic. So looks like the problem is just
isolated to ExecEvalPreOrderedDistinctSingle().

I've now pushed a fix for it and included your test. To get it to
crash it needed to be a byref aggregate without a strict transition
function. There are not too many of those, which is probably why
nobody noticed this before.

David