google-cloud-lib/src/main/java/com/streamsets/pipeline/stage/bigquery/destination/BigQueryTarget.java
private String getInsertIdForRecord(ELVars elVars, Record record) throws OnRecordErrorException {
    String recordId = null;
    RecordEL.setRecordInContext(elVars, record);
    try {
      if (!(StringUtils.isEmpty(conf.rowIdExpression))) {
        recordId = rowIdELEval.eval(elVars, conf.rowIdExpression, String.class);
        if (StringUtils.isEmpty(recordId)) {
          throw new OnRecordErrorException(record, Errors.BIGQUERY_15);
        }
      }
    } catch (ELEvalException e) {
      LOG.error("Error evaluating Row Expression EL", e);
      throw new OnRecordErrorException(record, Errors.BIGQUERY_10,e);
    }
    return recordId;
  }
private String getInsertIdForRecord(ELVars elVars, Record record) throws OnRecordErrorException {
    String recordId = null;
    RecordEL.setRecordInContext(elVars, record);
    try {
      if (!(StringUtils.isEmpty(conf.rowIdExpression))) {
        recordId = rowIdELEval.eval(elVars, conf.rowIdExpression, String.class);
        if (StringUtils.isEmpty(recordId)) {
          throw new OnRecordErrorException(record, Errors.BIGQUERY_15);
        }
      }
    } catch (ELEvalException e) {
      LOG.error("Error evaluating Row Expression EL", e);
      throw new OnRecordErrorException(record, Errors.BIGQUERY_10,e);
    }
    return recordId;
  }
Evaluate and obtain the row id if the expression is present or return null.