[jira] [Created] (HBASE-27637) Zero length value would cause value compressor read nothing nad not advance the position of the InputStream

["Duo Zhang (Jira)" <ji...@apache.org>]

Duo Zhang created HBASE-27637:
---------------------------------

             Summary: Zero length value would cause value compressor read nothing nad not advance the position of the InputStream
                 Key: HBASE-27637
                 URL: https://issues.apache.org/jira/browse/HBASE-27637
             Project: HBase
          Issue Type: Bug
          Components: dataloss, wal
            Reporter: Duo Zhang


This is a code sniff from the discussion of HBASE-27073

{code}
  public static void main(String[] args) throws Exception {
    CompressionContext ctx =
      new CompressionContext(LRUDictionary.class, false, false, true, Compression.Algorithm.GZ);
    ValueCompressor compressor = ctx.getValueCompressor();
    byte[] compressed = compressor.compress(new byte[0], 0, 0);
    System.out.println("compressed length: " + compressed.length);
    ByteArrayInputStream bis = new ByteArrayInputStream(compressed);
    int read = compressor.decompress(bis, compressed.length, new byte[0], 0, 0);
    System.out.println("read length: " + read);
    System.out.println("position: " + (compressed.length - bis.available()));
{code}

And the output is
{noformat}
compressed length: 20
read length: 0
position: 0
{noformat}

So it turns out that, when compressing, an empty array will still generate some output bytes but while reading, we will skip reading anything if we find the output length is zero, so next time when we read from the stream, we will start at a wrong position...



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