Re: Making Vars outer-join aware

On Mon, Aug 29, 2022 at 2:30 PM Richard Guo <guofenglinux(at)gmail(dot)com> wrote:

>
> On Fri, Aug 19, 2022 at 2:45 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
>> Here's a rebase up to HEAD, mainly to get the cfbot back in sync
>> as to what's the live patch.
>
>
> Noticed another different behavior from previous. When we try to reduce
> JOIN_LEFT to JOIN_ANTI, we want to know if the join's own quals are
> strict for any Var that was forced null by higher qual levels. We do
> that by checking whether local_nonnullable_vars and forced_null_vars
> overlap. However, the same Var from local_nonnullable_vars and
> forced_null_vars may be labeled with different varnullingrels. If that
> is the case, currently we would fail to tell they actually overlap.
>

I wonder why this is not noticed by regression tests. So I did some
search and it seems we do not have any test cases covering the
transformation we apply to reduce outer joins. I think maybe we should
add such cases in regression tests.

Thanks
Richard