private List<RelDataTypeField> getRelFields(List<SqlSchema.SqlField> fields) {
    List<RelDataTypeField> relFields = new ArrayList<>();

    for (SqlSchema.SqlField field : fields) {
      String fieldName = field.getFieldName();
      int fieldPos = field.getPosition();
      RelDataType dataType = getRelDataType(field.getFieldSchema());
      relFields.add(new RelDataTypeFieldImpl(fieldName, fieldPos, dataType));
    }

    return relFields;
  }
Class that converts the {@link SqlSchema} to Calcite relational schema
samza-sql/src/main/java/org/apache/samza/sql/planner/RelSchemaConverter.java