richardstartin commented on a change in pull request #7930:
URL: https://github.com/apache/pinot/pull/7930#discussion_r772657590
##########
File path:
pinot-segment-local/src/main/java/org/apache/pinot/segment/local/io/writer/impl/BaseChunkSVForwardIndexWriter.java
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@@ -74,15 +71,13 @@ protected BaseChunkSVForwardIndexWriter(File file,
ChunkCompressionType compress
int numDocsPerChunk, int chunkSize, int sizeOfEntry, int version)
throws IOException {
Preconditions.checkArgument(version == DEFAULT_VERSION || version ==
CURRENT_VERSION);
- _file = file;
- _headerEntryChunkOffsetSize = getHeaderEntryChunkOffsetSize(version);
- _dataOffset = headerSize(totalDocs, numDocsPerChunk,
_headerEntryChunkOffsetSize);
_chunkSize = chunkSize;
_chunkCompressor = ChunkCompressorFactory.getCompressor(compressionType);
+ _headerEntryChunkOffsetSize = getHeaderEntryChunkOffsetSize(version);
+ _dataOffset = writeHeader(compressionType, totalDocs, numDocsPerChunk,
sizeOfEntry, version);
_chunkBuffer = ByteBuffer.allocateDirect(chunkSize);
- _dataChannel = new RandomAccessFile(file, "rw").getChannel();
- _header = _dataChannel.map(FileChannel.MapMode.READ_WRITE, 0, _dataOffset);
- writeHeader(compressionType, totalDocs, numDocsPerChunk, sizeOfEntry,
version);
+ _compressedBuffer = ByteBuffer.allocateDirect(chunkSize * 2);
Review comment:
These bounds are specified by the compression codecs themselves. They
take the size of the uncompressed input as a parameter and produce the largest
possible compressed size for that input size. This isn't trying to optimise
something we don't know, but making proper use of compression libraries.
Playing devil's advocate, I'm curious how you know 2x is large enough for _any_
data? Wouldn't you prefer to use the compression library's specified bounds?
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