[GitHub] [pinot] mcvsubbu commented on a change in pull request #7930: Fix performance problem of base chunk forward index write

[GitBox <gi...@apache.org>]

mcvsubbu commented on a change in pull request #7930:
URL: https://github.com/apache/pinot/pull/7930#discussion_r772655331



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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:
       Do we have these bounds available at run time (preferably as an API)? Otherwise, instead of trying to optimize to something we don't know, we should revert to code that we know works in production environment




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