Re: ERROR: wrong varnullingrels (b 3) (expected (b)) for Var 2/1

On Mon, Jun 12, 2023 at 10:02 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Richard Guo <guofenglinux@gmail.com> writes:
> > Yeah, that makes sense.  process_subquery_nestloop_params is a better
> > place to do this adjustments.  +1 to v2 patch.
>
> Pushed, then.


Oh, wait ... It occurred to me that we may have this same issue with
Memoize cache keys.  In get_memoize_path we collect the cache keys from
innerpath's ppi_clauses and innerrel's lateral_vars, and the latter may
contain nullingrel markers that need adjustment.  As an example,
consider the query below

explain (costs off)
select * from onek t1
    left join onek t2 on true
    left join lateral
      (select * from onek t3 where t3.two = t2.two offset 0) s
      on t2.unique1 = 1;
ERROR:  wrong varnullingrels (b 3) (expected (b)) for Var 2/3

Attached is a patch that does the same adjustments to innerrel's
lateral_vars before they are added to MemoizePath->param_exprs.

I was wondering if there are more places that need this kind of
adjustments.  After some thoughts I believe the Memoize cache keys
should be the last one regarding adjustments to nestloop parameters.
AFAICS the lateral references in origin query would go to two places,
one is plan_params and the other is lateral_vars.  And now we've handled
both of them.

Thanks
Richard