@Override
        public Object get(int rowIndex) {

          if (rowIndex == MetadataColumns.ROW_POSITION.fieldId()) {
            if (fileRowOffset == Long.MIN_VALUE) {
              throw new UnsupportedOperationException("Can't provide row position for batch.");
            }
            return fileRowOffset + physicalPosition;
          } else {
            return vectorExtractRow.accessor(batch).apply(physicalPosition).apply(rowIndex);
          }
        }
File row position of the first row in this batch. Long.MIN_VALUE if unknown.
iceberg/iceberg-handler/src/main/java/org/apache/iceberg/mr/hive/vector/HiveBatchContext.java