[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #2182: fix: Sort with a lot of repetition values

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

Dandandan commented on code in PR #2182:
URL: https://github.com/apache/arrow-datafusion/pull/2182#discussion_r846405031


##########
datafusion/core/src/physical_plan/sorts/sort.rs:
##########
@@ -426,52 +426,78 @@ impl Iterator for SortedIterator {
         // Combine adjacent indexes from the same batch to make a slice,
         // for more efficient `extend` later.
         let mut last_batch_idx = 0;
-        let mut start_row_idx = 0;
-        let mut len = 0;
+        let mut indices_in_batch = vec![];
 
         let mut slices = vec![];
         for i in 0..current_size {
             let p = self.pos + i;
             let c_index = self.indices.value(p) as usize;
             let ci = self.composite[c_index];
 
-            if len == 0 {
+            if indices_in_batch.is_empty() {
                 last_batch_idx = ci.batch_idx;
-                start_row_idx = ci.row_idx;
-                len = 1;
+                indices_in_batch.push(ci.row_idx);
             } else if ci.batch_idx == last_batch_idx {
-                len += 1;
-                // since we have pre-sort each of the incoming batches,
-                // so if we witnessed a wrong order of indexes from the same batch,
-                // it must be of the same key with the row pointed by start_row_index.
-                start_row_idx = min(start_row_idx, ci.row_idx);
+                indices_in_batch.push(ci.row_idx);
             } else {
-                slices.push(CompositeSlice {
-                    batch_idx: last_batch_idx,
-                    start_row_idx,
-                    len,
-                });
+                let indices = indices_in_batch.drain(..).collect::<Vec<_>>();
+                group_indices(last_batch_idx, indices, &mut slices);

Review Comment:
   Could just pass `indices_in_batch` + `clear` instead of drain/collect?



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