[GitHub] [iceberg] rdblue commented on a change in pull request #1334: Fix Error Prone ByteBuffer warnings

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

rdblue commented on a change in pull request #1334:
URL: https://github.com/apache/iceberg/pull/1334#discussion_r470758731



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File path: data/src/main/java/org/apache/iceberg/data/orc/GenericOrcWriters.java
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@@ -231,7 +231,24 @@ public void nonNullWrite(int rowId, String data, ColumnVector output) {
 
     @Override
     public void nonNullWrite(int rowId, ByteBuffer data, ColumnVector output) {
-      ((BytesColumnVector) output).setRef(rowId, data.array(), 0, data.array().length);
+      // We technically can't be sure if the ByteBuffer coming in is on or off
+      // heap so we cannot safely call `.array()` on it without first checking
+      // via the method ByteBuffer.hasArray().
+      // See: https://errorprone.info/bugpattern/ByteBufferBackingArray
+      //
+      // When there is a backing heap based byte array, we avoided the overhead of
+      // copying, which is especially important for small byte buffers.
+      //
+      // TODO - This copy slows it down, perhap unnecessarily. Is there any other way to tell, or no?
+      //        My guess is no, if I consider things like VectorizedOrcReaders on Spark.
+      if (data.hasArray()) {
+        ((BytesColumnVector) output).setRef(rowId, data.array(), 0, data.array().length);

Review comment:
       This is not a correct use of `ByteBuffer` because it doesn't use `arrayOffset` or `remaining`. I think the current version must work because Spark returns new arrays that we wrap in `ByteBuffer`, but if the goal here is to make this accept any `ByteBuffer` then we should account for cases where the buffer is not simply the entire backing array.




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