[GitHub] [arrow-datafusion] e-dard commented on a change in pull request #722: perf: improve performance of `SortPreservingMergeExec` operator

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

e-dard commented on a change in pull request #722:
URL: https://github.com/apache/arrow-datafusion/pull/722#discussion_r668989904



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File path: datafusion/src/physical_plan/sort_preserving_merge.rs
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@@ -246,7 +274,19 @@ impl SortKeyCursor {
             .zip(other.columns.iter())
             .zip(options.iter());
 
-        for ((l, r), sort_options) in zipped {
+        // Recall or initialise a collection of comparators for comparing
+        // columnar arrays of this cursor and "other".
+        let cmp = self
+            .batch_comparators
+            .entry(other.batch_idx)
+            .or_insert_with(|| Vec::with_capacity(other.columns.len()));

Review comment:
       Ha. Yeah that's how I had it but you have to re-create the iterator. I'm happy to go with whatever




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