[GitHub] [iceberg] stevenzwu commented on a diff in pull request #6304: API, Core: Add groupingKey to ScanTaskGroup

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

stevenzwu commented on code in PR #6304:
URL: https://github.com/apache/iceberg/pull/6304#discussion_r1034129295


##########
api/src/main/java/org/apache/iceberg/ScanTaskGroup.java:
##########
@@ -26,6 +26,24 @@
  * @param <T> the type of scan tasks
  */
 public interface ScanTaskGroup<T extends ScanTask> extends ScanTask {
+  /**
+   * Returns a grouping key for this task group.
+   *
+   * <p>Tasks may produce records that belong to a specific group of data (e.g. partition). It may
+   * be beneficial to preserve that grouping while combining tasks into groups if query engines can
+   * leverage that information to avoid shuffles. Grouping keys indicate how data is split between
+   * different task groups. The grouping key type is determined at planning time and is identical
+   * across all task groups produced by a scan.
+   *
+   * <p>All records produced by tasks in this group are guaranteed to have the reported grouping
+   * key. Implementations should return an empty struct if the data grouping is random or unknown.
+   *
+   * @return a grouping key for this task group
+   */
+  default StructLike groupingKey() {

Review Comment:
   +1. matches better with the interface name of `ScanTaskGroup`



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