Samarth Jain created PARQUET-1641: ------------------------------------- Summary: Parquet pages for different columns cannot be read in parallel Key: PARQUET-1641 URL: https://issues.apache.org/jira/browse/PARQUET-1641 Project: Parquet Issue Type: Improvement Reporter: Samarth Jain
All ColumnChunkPageReader instances use the same decompressor. [https://github.com/apache/parquet-mr/blob/master/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java#L1286] <code> BytesInputDecompressor decompressor = options.getCodecFactory().getDecompressor(descriptor.metadata.getCodec()); return new ColumnChunkPageReader(decompressor, pagesInChunk, dictionaryPage); </code> The CodecFactory caches the decompressors for every codec type returning the same instance on every getCompressor(codecName) call. See the caching happening here: [https://github.com/apache/parquet-mr/blob/master/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/CodecFactory.java#L197] <code> @Override public BytesDecompressor getDecompressor(CompressionCodecName codecName) { BytesDecompressor decomp = decompressors.get(codecName); if (decomp == null) { decomp = createDecompressor(codecName); decompressors.put(codecName, decomp); } return decomp; } </code> If multiple threads try to read the pages belonging to different columns, they run into thread safety issues. This issue prevents increasing the throughput at which applications can read parquet data by parallelizing page reads. -- This message was sent by Atlassian Jira (v8.3.2#803003)