Re: A performance issue with Memoize

At first I wondered if we should assume that the same param expr must
have the same equality operator. If not, we should also check the
operator to tell if the cache key is a duplicate, like

-           if (!list_member(*param_exprs, expr))
+           if (!list_member(*param_exprs, expr) ||
+               !list_member_oid(*operators, hasheqoperator))

But after looking at how rinfo->left_hasheqoperator/right_hasheqoperator
is set, it seems we can assume that: the operator is from the type cache
entry which is fetched according to the expr datatype.

So I think the patch makes sense.  +1.

Thanks
Richard