@Override public void onMatch(RelOptRuleCall call) {
      Filter filter = call.rel(0);
      Join join = call.rel(1);
      perform(call, filter, join);
    }
Rule that tries to push the stream side of the filter expressions into the input of the join.
samza-sql/src/main/java/org/apache/samza/sql/planner/SamzaSqlFilterRemoteJoinRule.java