zachdisc commented on code in PR #9731:
URL: https://github.com/apache/iceberg/pull/9731#discussion_r1500927289


##########
spark/v3.5/spark/src/main/java/org/apache/iceberg/spark/actions/RewriteManifestsSparkAction.java:
##########
@@ -250,12 +282,40 @@ private List<ManifestFile> writeUnpartitionedManifests(
   private List<ManifestFile> writePartitionedManifests(
       ManifestContent content, Dataset<Row> manifestEntryDF, int numManifests) 
{
 
+    // Extract desired clustering/sorting criteria into a dedicated column
+    Dataset<Row> clusteredManifestEntryDF;
+    String clusteringColumnName = "__clustering_column__";
+
+    if (partitionSortColumns != null) {
+      LOG.info(
+          "Sorting manifests for specId {} by partition columns in order of {} 
",
+          spec.specId(),
+          partitionSortColumns);
+
+      // Map the top level partition column names to the column name 
referenced within the manifest
+      // entry dataframe
+      Column[] actualPartitionColumns =
+          partitionSortColumns.stream()
+              .map(p -> col("data_file.partition." + p))
+              .toArray(Column[]::new);
+
+      // Form a new temporary column to sort/cluster manifests on, based on 
the custom sort
+      // order provided
+      clusteredManifestEntryDF =
+          manifestEntryDF.withColumn(
+              clusteringColumnName, functions.struct(actualPartitionColumns));
+    } else {
+      clusteredManifestEntryDF =
+          manifestEntryDF.withColumn(clusteringColumnName, 
col("data_file.partition"));
+    }
+
     return withReusableDS(
-        manifestEntryDF,
+        clusteredManifestEntryDF,
         df -> {
           WriteManifests<?> writeFunc = newWriteManifestsFunc(content, 
df.schema());
-          Column partitionColumn = df.col("data_file.partition");
-          Dataset<Row> transformedDF = repartitionAndSort(df, partitionColumn, 
numManifests);
+          Column partitionColumn = df.col(clusteringColumnName);
+          Dataset<Row> transformedDF =
+              repartitionAndSort(df, partitionColumn, 
numManifests).drop(clusteringColumnName);

Review Comment:
   Happy to make that change, but IMHO the API is indicating how the entire 
forest of manifests is sorted, not necessarily how each tree is sorted. Like, 
its sorting the `manifest_list` entries in the end, while the `manifest_files` 
are sorted further within that. Thoughts?
   
   Though, I suppose it isn't really `sort`ing the whole forest, it is 
`clustering`. 



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