I agree that extensibility might be helpful, however: 1) I do not like the idea of XOR-based hash code, because it would make ($1=$1) have the same hashcode as ($2=$2) and so on. 2) "$2 > $1 is reordered to $1 < $2, so that predicate a > b and b < a can be reduced to a > b." This reverting can easily happen as rule does its transformations (e.g. swap join order and so on). That is why ability to normalize < into > helps like it helps for $1=$2 vs $2=$1
>when just computing the hash code? What I do not like with the current code is it does perform compute-intensive operations when calling equals. Previous code (the one from CALCITE-2450) never computed the normalization multiple times per RexNode. It looks like now we losing that feature. Vladimir
