Re: Check lateral references within PHVs for memoize cache keys

On Sun, Jul 9, 2023 at 12:17 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:

> I just pushed a fix for this. Thanks for reporting it.

BTW, I noticed a typo in the comment inside paraminfo_get_equal_hashops.

foreach(lc, innerrel->lateral_vars)
{
Node *expr = (Node *) lfirst(lc);
TypeCacheEntry *typentry;

/* Reject if there are any volatile functions in PHVs */
if (contain_volatile_functions(expr))
{
list_free(*operators);
list_free(*param_exprs);
return false;
}

The expressions in RelOptInfo.lateral_vars are not necessarily from
PHVs. For instance

explain (costs off)
select * from t t1 join
lateral (select * from t t2 where t1.a = t2.a offset 0) on true;
QUERY PLAN
----------------------------------
Nested Loop
-> Seq Scan on t t1
-> Memoize
Cache Key: t1.a
Cache Mode: binary
-> Seq Scan on t t2
Filter: (t1.a = a)
(7 rows)

The lateral Var 't1.a' comes from the lateral subquery, not PHV.

This seems a typo from 63e4f13d. How about we change it to the below?

- /* Reject if there are any volatile functions in PHVs */
+ /* Reject if there are any volatile functions in lateral vars */

Thanks
Richard