jayzhan211 commented on code in PR #13133:
URL: https://github.com/apache/datafusion/pull/13133#discussion_r1818032540
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datafusion/physical-plan/src/sorts/merge.rs:
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@@ -327,16 +409,79 @@ impl<C: CursorValues> SortPreservingMergeStream<C> {
self.loser_tree_adjusted = true;
}
- /// Attempts to update the loser tree, following winner replacement, if
possible
+ /// Resets the poll count by incrementing the reset epoch.
+ fn reset_poll_counts(&mut self) {
+ self.current_reset_epoch += 1;
+ }
+
+ /// Handles tie-breaking logic during the adjustment of the loser tree.
+ ///
+ /// When comparing elements from multiple partitions in the
`update_loser_tree` process, a tie can occur
+ /// between the current winner and a challenger. This function is invoked
when such a tie needs to be
+ /// resolved according to the round-robin tie-breaker mode.
+ ///
+ /// If round-robin tie-breaking is not active, it is enabled, and the poll
counts for all elements are reset.
+ /// The function then compares the poll counts of the current winner and
the challenger:
+ /// - If the winner remains at the top after the final comparison, it
increments the winner's poll count.
+ /// - If the challenger has a higher poll count than the winner, the
challenger is declared the new winner.
Review Comment:
Sure
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