lyne7-sc commented on code in PR #20243:
URL: https://github.com/apache/datafusion/pull/20243#discussion_r2788523390
##########
datafusion/functions-nested/src/set_ops.rs:
##########
@@ -358,69 +364,84 @@ fn generic_set_lists<OffsetSize: OffsetSizeTrait>(
"{set_op:?} is not implemented for '{l:?}' and '{r:?}'"
);
- let mut offsets = vec![OffsetSize::usize_as(0)];
- let mut new_arrays = vec![];
+ // Convert all values to rows in batch for performance.
let converter = RowConverter::new(vec![SortField::new(l.value_type())])?;
- for (l_arr, r_arr) in l.iter().zip(r.iter()) {
- let last_offset = *offsets.last().unwrap();
-
- let (l_values, r_values) = match (l_arr, r_arr) {
- (Some(l_arr), Some(r_arr)) => (
- converter.convert_columns(&[l_arr])?,
- converter.convert_columns(&[r_arr])?,
- ),
- _ => {
- offsets.push(last_offset);
- continue;
- }
- };
-
- let l_iter = l_values.iter().sorted().dedup();
- let values_set: HashSet<_> = l_iter.clone().collect();
- let mut rows = if set_op == SetOp::Union {
- l_iter.collect()
- } else {
- vec![]
- };
+ let rows_l = converter.convert_columns(&[Arc::clone(l.values())])?;
+ let rows_r = converter.convert_columns(&[Arc::clone(r.values())])?;
+ let l_offsets = l.value_offsets();
+ let r_offsets = r.value_offsets();
+
+ let mut result_offsets = Vec::with_capacity(l.len() + 1);
+ result_offsets.push(OffsetSize::usize_as(0));
+ let mut final_rows = Vec::with_capacity(rows_l.num_rows());
+
+ // Reuse hash sets across iterations
+ let mut seen = HashSet::new();
+ let mut r_set = HashSet::new();
+ for i in 0..l.len() {
+ let last_offset = *result_offsets.last().unwrap();
+
+ if l.is_null(i) || r.is_null(i) {
+ result_offsets.push(last_offset);
+ continue;
+ }
- for r_val in r_values.iter().sorted().dedup() {
- match set_op {
- SetOp::Union => {
- if !values_set.contains(&r_val) {
- rows.push(r_val);
+ let l_start = l_offsets[i].as_usize();
+ let l_end = l_offsets[i + 1].as_usize();
+ let r_start = r_offsets[i].as_usize();
+ let r_end = r_offsets[i + 1].as_usize();
+
+ let mut count = 0usize;
+ // Clear sets for reuse
+ seen.clear();
+ r_set.clear();
+
+ match set_op {
+ SetOp::Union => {
+ for idx in l_start..l_end {
+ let row = rows_l.row(idx);
+ if seen.insert(row) {
+ final_rows.push(row);
+ count += 1;
}
}
- SetOp::Intersect => {
- if values_set.contains(&r_val) {
- rows.push(r_val);
+ for idx in r_start..r_end {
+ let row = rows_r.row(idx);
+ if seen.insert(row) {
+ final_rows.push(row);
+ count += 1;
}
}
}
- }
-
- offsets.push(last_offset + OffsetSize::usize_as(rows.len()));
- let arrays = converter.convert_rows(rows)?;
- let array = match arrays.first() {
- Some(array) => Arc::clone(array),
- None => {
- return internal_err!("{set_op}: failed to get array from
rows");
+ SetOp::Intersect => {
+ // Build hash set from right array for lookup table
+ // then iterator left array to find common elements.
Review Comment:
now building the HashSet from the shorter array and iterating over the
longer one, good catch.
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