[GitHub] [flink] luoyuxia commented on a diff in pull request #20830: [FLINK-29271]Change to byte array from bytebuffer to improve performance and compatible direct byte buffers

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

luoyuxia commented on code in PR #20830:
URL: https://github.com/apache/flink/pull/20830#discussion_r1002872635


##########
flink-formats/flink-parquet/src/main/java/org/apache/flink/formats/parquet/vector/reader/RunLengthDecoder.java:
##########
@@ -265,8 +265,16 @@ void readNextGroup() {
                     while (valueIndex < this.currentCount) {
                         // values are bit packed 8 at a time, so reading bitWidth will always work
                         ByteBuffer buffer = in.slice(bitWidth);
-                        this.packer.unpack8Values(
-                                buffer, buffer.position(), this.currentBuffer, valueIndex);
+                        if (buffer.hasArray()) {
+                            this.packer.unpack8Values(

Review Comment:
   I'm wondering why this changes will improve perfermance. IIUC, from the code
   ```java
   public void unpack8Values(final byte[] input, final int inPos, final int[] output, final int outPos) {
       unpack8Values(ByteBuffer.wrap(input), inPos, output, outPos);
     }
   ```
    the method just delegates to `unpack8Values` and it needs extra `ByteBuffer.wrap(input)`.
   Could you please explain a little bit?



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