@Override
    public void onMatch(RelOptRuleCall call) {
      Join join = call.rel(0);
      super.perform(call, null, join);
    }
Rule that tries to push filter expressions into a join condition and into
the inputs of the join.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveFilterJoinRule.java