Re: Making Vars outer-join aware

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. As
an example, consider 'b.i' in the query below

# explain (costs off) select * from a left join b on a.i = b.i where b.i is
null;
QUERY PLAN
---------------------------
Hash Left Join
Hash Cond: (a.i = b.i)
Filter: (b.i IS NULL)
-> Seq Scan on a
-> Hash
-> Seq Scan on b
(6 rows)

Thanks
Richard