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perf: Improve median with no grouping by 2X #14399

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Merged
merged 2 commits into from
Feb 2, 2025
Merged

perf: Improve median with no grouping by 2X #14399

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ee6fe71
improve median() no grouping case
2010YOUY01 Feb 1, 2025
ab4eeaa
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2010YOUY01 Feb 1, 2025
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26 changes: 19 additions & 7 deletions datafusion/functions-aggregate/src/median.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -242,14 +242,26 @@ impl<T: ArrowNumericType> Debug for MedianAccumulator<T> {

impl<T: ArrowNumericType> Accumulator for MedianAccumulator<T> {
fn state(&mut self) -> Result<Vec<ScalarValue>> {
let all_values = self
.all_values
.iter()
.map(|x| ScalarValue::new_primitive::<T>(Some(*x), &self.data_type))
.collect::<Result<Vec<_>>>()?;
// Convert `all_values` to `ListArray` and return a single List ScalarValue

let arr = ScalarValue::new_list_nullable(&all_values, &self.data_type);
Ok(vec![ScalarValue::List(arr)])
// Build offsets
let offsets =
OffsetBuffer::new(ScalarBuffer::from(vec![0, self.all_values.len() as i32]));

// Build inner array
let values_array =
PrimitiveArray::<T>::new(ScalarBuffer::from(self.all_values.clone()), None)
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@Rachelint Rachelint Feb 1, 2025

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Seems we can take all_values directly, and reduce the allocation?

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@2010YOUY01 2010YOUY01 Feb 1, 2025

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updated, thanks!

.with_data_type(self.data_type.clone());

// Build the result list array
let list_array = ListArray::new(
Arc::new(Field::new_list_field(self.data_type.clone(), true)),
offsets,
Arc::new(values_array),
None,
);

Ok(vec![ScalarValue::List(Arc::new(list_array))])
}

fn update_batch(&mut self, values: &[ArrayRef]) -> Result<()> {
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