private static Schema prepareSchemaForDeleteFilter(Schema schema) {
    List<Types.NestedField> columns = Lists.newArrayList(schema.columns());
    columns.add(MetadataColumns.IS_DELETED);
    return new Schema(columns);
  }
We need to add IS_DELETED metadata field so that DeleteFilter marks deleted rows rather than filering them out.
@param schema original schema
@return adjusted schema
iceberg/iceberg-handler/src/main/java/org/apache/iceberg/mr/hive/vector/HiveVectorizedReader.java