[GitHub] [iceberg] danielcweeks commented on a diff in pull request #7731: Core: Implement adaptive split planning in core.

["danielcweeks (via GitHub)" <gi...@apache.org>]

danielcweeks commented on code in PR #7731:
URL: https://github.com/apache/iceberg/pull/7731#discussion_r1209470679


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core/src/main/java/org/apache/iceberg/util/TableScanUtil.java:
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@@ -79,6 +88,44 @@ public static CloseableIterable<FileScanTask> splitFiles(
     return CloseableIterable.combine(splitTasks, tasks);
   }
 
+  /**
+   * Produces {@link CombinedScanTask combined tasks} from an iterable of {@link FileScanTask file
+   * tasks}, using an adaptive target split size that targets a minimum number of tasks
+   * (parallelism).
+   *
+   * @param files incoming iterable of file tasks
+   * @param parallelism target minimum number of tasks
+   * @param splitSize target split size
+   * @param lookback bin packing lookback
+   * @param openFileCost minimum file cost
+   * @return an iterable of combined tasks
+   */
+  public static CloseableIterable<CombinedScanTask> planTasksAdaptive(
+      CloseableIterable<FileScanTask> files,
+      int parallelism,
+      long splitSize,
+      int lookback,
+      long openFileCost) {
+
+    validatePlanningArguments(splitSize, lookback, openFileCost);
+
+    Function<FileScanTask, Long> weightFunc =
+        file ->
+            Math.max(
+                file.length()
+                    + file.deletes().stream().mapToLong(ContentFile::fileSizeInBytes).sum(),
+                (1 + file.deletes().size()) * openFileCost);

Review Comment:
   This feels like it's too large for a min split size.  Either that or we should take into account what the row group size is actually configured to.  For example, if the row group was set to 8MB, then we still wouldn't be able to achieve maximum parallelism because of this arbitrary default.



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