[GitHub] [hbase] shahrs87 commented on a change in pull request #3244: HBASE-25869 WAL value compression

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

shahrs87 commented on a change in pull request #3244:
URL: https://github.com/apache/hbase/pull/3244#discussion_r629708006



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File path: hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/WALCellCodec.java
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@@ -256,6 +278,26 @@ public void write(Cell cell) throws IOException {
         }
       }
     }
+
+    private byte[] compressValue(Cell cell) throws IOException {
+      byte[] buffer = new byte[4096];
+      ByteArrayOutputStream baos = new ByteArrayOutputStream();
+      Deflater deflater = compression.getValueCompressor().getDeflater();
+      deflater.setInput(cell.getValueArray(), cell.getValueOffset(), cell.getValueLength());
+      boolean finished = false;
+      do {
+        int bytesOut = deflater.deflate(buffer);
+        if (bytesOut > 0) {
+          baos.write(buffer, 0, bytesOut);
+        } else {
+          bytesOut = deflater.deflate(buffer, 0, buffer.length, Deflater.SYNC_FLUSH);

Review comment:
       If we reach this else condition that means we have compressed all the data and written to ByteArrayOutputStream. 
   Now in else condition, we are sure that bytesOut will be 0. We are not resetting `buffer`  anywhere. So for the last chunk of Cell's value whose size <= 4096, will we be compressing them twice ?
   @apurtell  It is entirely possible that I misunderstood something. Please correct me if that is the case. Thank you !




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