rluvaton commented on code in PR #18152:
URL: https://github.com/apache/datafusion/pull/18152#discussion_r2466038692
##########
datafusion/physical-expr/src/expressions/case.rs:
##########
@@ -196,82 +577,135 @@ impl CaseExpr {
/// END
fn case_when_with_expr(&self, batch: &RecordBatch) ->
Result<ColumnarValue> {
let return_type = self.data_type(&batch.schema())?;
- let expr = self.expr.as_ref().unwrap();
- let base_value = expr.evaluate(batch)?;
- let base_value = base_value.into_array(batch.num_rows())?;
+ let mut result_builder = ResultBuilder::new(&return_type,
batch.num_rows());
+
+ // `remainder_rows` contains the indices of the rows that need to be
evaluated
+ let mut remainder_rows: ArrayRef =
+ Arc::new(UInt32Array::from_iter_values(0..batch.num_rows() as
u32));
+ // `remainder_batch` contains the rows themselves that need to be
evaluated
+ let mut remainder_batch = Cow::Borrowed(batch);
+
+ // evaluate the base expression
+ let mut base_value = self
+ .expr
+ .as_ref()
+ .unwrap()
+ .evaluate(batch)?
+ .into_array(batch.num_rows())?;
+
+ // Fill in a result value already for rows where the base expression
value is null
+ // Since each when expression is tested against the base expression
using the equality
+ // operator, null base values can never match any when expression. `x
= NULL` is falsy,
+ // for all possible values of `x`.
let base_nulls = is_null(base_value.as_ref())?;
+ if base_nulls.true_count() > 0 {
Review Comment:
Nit: this have unnecessary computation, you can access the number of nulls
by using `base_value.null_count()`
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