@Override public Optional<ParquetDataColumnReader> visit(
              StringLogicalTypeAnnotation logicalTypeAnnotation) {
            return isDict ? Optional
                .of(new TypesFromStringPageReader(dictionary, length)) : Optional
                .of(new TypesFromStringPageReader(valuesReader, length));
          }
The reader who reads from the underlying UTF8 string.
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/vector/ParquetDataColumnReaderFactory.java