Dandandan commented on code in PR #15697:
URL: https://github.com/apache/datafusion/pull/15697#discussion_r2041528193
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datafusion/physical-plan/src/topk/mod.rs:
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@@ -202,27 +204,99 @@ impl TopK {
})
.collect::<Result<Vec<_>>>()?;
+ // selected indices
+ let mut selected_rows = None;
+
+ // If the heap doesn't have k elements yet, we can't create thresholds
+ if let Some(max_row) = self.heap.max() {
+ // Get the batch that contains the max row
+ let batch_entry = match self.heap.store.get(max_row.batch_id) {
+ Some(entry) => entry,
+ None => return internal_err!("Invalid batch ID in TopKRow"),
+ };
+
+ // Extract threshold values for each sort expression
+ // TODO: create a filter for each key that respects lexical
ordering
Review Comment:
Yes, it might very well be evaluating all keys is more expensive than
converting to rows.
It might benefit from optimizations like in
https://github.com/apache/datafusion/pull/15694 to avoid evaluating the
expression for values already filtered out...
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