[GitHub] [iceberg] szehon-ho commented on a diff in pull request #7703: Spark 3.4: Support fanout writers in SparkPositionDeltaWrite

["szehon-ho (via GitHub)" <gi...@apache.org>]

szehon-ho commented on code in PR #7703:
URL: https://github.com/apache/iceberg/pull/7703#discussion_r1206054291


##########
spark/v3.4/spark/src/test/java/org/apache/iceberg/spark/TestSparkDistributionAndOrderingUtil.java:
##########
@@ -1805,23 +1805,32 @@ public void testRangeCopyOnWriteMergePartitionedSortedTable() {
   // -------------------------------------------------------------------------
   // delete mode is NOT SET -> CLUSTER BY _spec_id, _partition, _file +
   //                           LOCALLY ORDERED BY _spec_id, _partition, _file, _pos
+  // delete mode is NOT SET (fanout) -> CLUSTER BY _spec_id, _partition, _file + empty ordering

Review Comment:
   Probably annoying to add another example with ORDERED BY, but is it still correct with  "ORDERED" above?    Will it not be empty_ordering?



##########
spark/v3.4/spark/src/main/java/org/apache/iceberg/spark/source/SparkPositionDeltaWrite.java:
##########
@@ -389,10 +391,44 @@ protected Map<Integer, StructProjection> buildPartitionProjections(
 
       return partitionProjections;
     }
+
+    // use the fanout writer only if enabled and the input is unordered
+    protected PartitioningWriter<InternalRow, DataWriteResult> newDataWriter(
+        Table table, SparkFileWriterFactory writers, OutputFileFactory files, Context context) {
+
+      FileIO io = table.io();
+      boolean fanoutEnabled = context.fanoutWriterEnabled();
+      boolean inputOrdered = context.inputOrdered();
+      long targetFileSize = context.targetDataFileSize();
+
+      if (fanoutEnabled && !inputOrdered) {
+        return new FanoutDataWriter<>(writers, files, io, targetFileSize);
+      } else {
+        return new ClusteredDataWriter<>(writers, files, io, targetFileSize);
+      }
+    }
+
+    // the spec requires position deletes to be ordered by file and position
+    // use a fanout writer if the input is unordered no matter whether fanout writers are enabled
+    // clustered writers only validate records for the same spec/paritition are co-located,

Review Comment:
   Optional: clustered writers only validate records for the same spec/paritition are co-located which is not enough for position deletes => clustered writers assume that the position deletes are already ordered by file and position?
   
   (the validation seems a bit orthogonal to previous sentence.   I dont mind putting it in a as well somewhere, but doesnt seem its in the other comment in newDataWriter, so hence thinking its better to omit)



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