@Override
      public RexNode visitInputRef(RexInputRef inputRef) {
        refCollector.add(inputRef);
        return inputRef;
      }
Translator to translate the LogicalJoin node in the relational graph to the corresponding StreamGraph
implementation.
Join is supported with the following caveats:
  1. Only stream-table joins are supported. No stream-stream joins.
  2. Only Equi-joins are supported. No theta-joins.
  3. Inner joins, Left and Right outer joins are supported. No cross joins, full outer joins or natural joins.
  4. Join condition with a constant is not supported.
  5. Compound join condition with only AND operator is supported. AND operator with a constant is not supported. No
     support for OR operator or any other operator in the join condition.
For local table, we always repartition both the stream to be joined and the stream denoted as table by the key(s)
specified in the join condition.
samza-sql/src/main/java/org/apache/samza/sql/translator/JoinTranslator.java