protected boolean isOptional(RelSchemaProvider outputRelSchemaProvider, String outputFieldName,
      RelRecordType projectRecord) {
    return false;
  }
Determine if validation needs to be done on Calcite plan based on the schema provider and schema converter.
@param relRoot
@param sink
@param outputSchemaProvider
@param ouputRelSchemaConverter
@return if the validation needs to be skipped
samza-sql/src/main/java/org/apache/samza/sql/planner/SamzaSqlValidator.java