pepijnve commented on code in PR #18152:
URL: https://github.com/apache/datafusion/pull/18152#discussion_r2466213717
##########
datafusion/physical-expr/src/expressions/case.rs:
##########
@@ -283,70 +717,81 @@ impl CaseExpr {
/// END
fn case_when_no_expr(&self, batch: &RecordBatch) -> Result<ColumnarValue> {
let return_type = self.data_type(&batch.schema())?;
+ let mut result_builder = ResultBuilder::new(&return_type,
batch.num_rows());
- // start with nulls as default output
- let mut current_value = new_null_array(&return_type, batch.num_rows());
- let mut remainder = BooleanArray::from(vec![true; batch.num_rows()]);
- let mut remainder_count = batch.num_rows();
- for i in 0..self.when_then_expr.len() {
- // If there are no rows left to process, break out of the loop
early
- if remainder_count == 0 {
- break;
- }
+ // `remainder_rows` contains the indices of the rows that need to be
evaluated
+ let mut remainder_rows: ArrayRef =
+ Arc::new(UInt32Array::from_iter(0..batch.num_rows() as u32));
+ // `remainder_batch` contains the rows themselves that need to be
evaluated
+ let mut remainder_batch = Cow::Borrowed(batch);
+ for i in 0..self.when_then_expr.len() {
+ // Evaluate the 'when' predicate for the remainder batch
+ // This results in a boolean array with the same length as the
remaining number of rows
let when_predicate = &self.when_then_expr[i].0;
- let when_value = when_predicate.evaluate_selection(batch,
&remainder)?;
- let when_value = when_value.into_array(batch.num_rows())?;
+ let when_value = when_predicate
+ .evaluate(&remainder_batch)?
+ .into_array(remainder_batch.num_rows())?;
Review Comment:
I actually considered this one, but that got me wondering when this would
ever actually happen. Whatever the predicate is would have to be able to figure
out that it's always true or always false. How often does that actually occur
in practice? And is this not likely to get eliminated by the optimiser? I ended
up keeping it simple for now.
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