Dandandan commented on code in PR #13134:
URL: https://github.com/apache/datafusion/pull/13134#discussion_r1821458520


##########
datafusion/physical-plan/src/joins/sort_merge_join.rs:
##########
@@ -784,6 +790,29 @@ fn get_corrected_filter_mask(
             corrected_mask.extend(vec![Some(false); null_matched]);
             Some(corrected_mask.finish())
         }
+        JoinType::LeftMark => {
+            for i in 0..row_indices_length {
+                let last_index =
+                    last_index_for_row(i, row_indices, batch_ids, 
row_indices_length);
+                if filter_mask.value(i) && !seen_true {

Review Comment:
   The paper
   
http://btw2017.informatik.uni-stuttgart.de/slidesandpapers/F1-10-37/paper_web.pdf
   is quite helpful to understand it.
   
   The issue explains as well a for queries like `exists` a join + distinct 
will be needed, this will surely be less efficient than the mark join. 



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