@Override
    public RexNode ensureType(RelDataType type, RexNode node, boolean matchNullability) {
      return node;
    }
Since Drill has different mechanism and rules for implicit casting,
ensureType() is overridden to avoid conflicting cast functions being added to the expressions.
samza-sql/src/main/java/org/apache/samza/sql/translator/TranslatorContext.java