[GitHub] [parquet-mr] steveloughran commented on a diff in pull request #951: PARQUET-2134: Fix type checking in HadoopStreams.wrap

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

steveloughran commented on code in PR #951:
URL: https://github.com/apache/parquet-mr/pull/951#discussion_r890388928


##########
parquet-hadoop/src/main/java/org/apache/parquet/hadoop/util/HadoopStreams.java:
##########
@@ -51,7 +52,7 @@ public class HadoopStreams {
   public static SeekableInputStream wrap(FSDataInputStream stream) {
     Objects.requireNonNull(stream, "Cannot wrap a null input stream");
     if (byteBufferReadableClass != null && h2SeekableConstructor != null &&
-        byteBufferReadableClass.isInstance(stream.getWrappedStream())) {
+        isWrappedStreamByteBufferReadable(stream)) {

Review Comment:
   this is really going into the internals of the hadoop classes and potentially tricky if there is any dynamic decision making in the inner class. The good news there is I don't see anything doing that.
   
   there is a way to ask (hadoop 3.2+) if a stream does support the API before calling, using the StreamCapabilities interface.
   https://issues.apache.org/jira/browse/HDFS-14111
   
   ```java
   if (stream.hasCapability( "in:readbytebuffer") {
     // stream is confident it has the api
   ) else {
     // do the checking of the inner class
   }



##########
parquet-hadoop/src/main/java/org/apache/parquet/hadoop/util/HadoopStreams.java:
##########
@@ -66,6 +67,15 @@ public static SeekableInputStream wrap(FSDataInputStream stream) {
     }
   }
 
+  private static boolean isWrappedStreamByteBufferReadable(FSDataInputStream stream) {
+    InputStream wrapped = stream.getWrappedStream();
+    if (wrapped instanceof FSDataInputStream) {
+      return isWrappedStreamByteBufferReadable(((FSDataInputStream) wrapped));

Review Comment:
   you can't. the inner stream is set in the constructor, so cannot take the not-yet-constructed class as an argument.



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