doki23 commented on a change in pull request #2068:
URL: https://github.com/apache/arrow-datafusion/pull/2068#discussion_r833893451
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File path: datafusion-physical-expr/src/expressions/case.rs
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@@ -323,24 +323,19 @@ impl CaseExpr {
let base_value = expr.evaluate(batch)?;
let base_type = expr.data_type(&batch.schema())?;
let base_value = base_value.into_array(batch.num_rows());
+ let base_nulls = is_null(base_value.as_ref())?;
- // start with the else condition, or nulls
- let mut current_value: Option<ArrayRef> = if let Some(e) =
&self.else_expr {
- // keep `else_expr`'s data type and return type consistent
- let expr = try_cast(e.clone(), &*batch.schema(),
return_type.clone())
- .unwrap_or_else(|_| e.clone());
- Some(expr.evaluate(batch)?.into_array(batch.num_rows()))
- } else {
- Some(new_null_array(&return_type, batch.num_rows()))
- };
-
- // walk backwards through the when/then expressions
- for i in (0..self.when_then_expr.len()).rev() {
+ // start with nulls as default output
+ let mut current_value = new_null_array(&return_type, batch.num_rows());
+ // We only consider non-null values while comparing with whens
+ let mut remainder = not(&base_nulls)?;
+ for i in 0..self.when_then_expr.len() {
let i = i as usize;
- let when_value = self.when_then_expr[i].0.evaluate(batch)?;
+ let when_value = self.when_then_expr[i]
+ .0
+ .evaluate_selection(batch, &remainder)?;
Review comment:
👍 Great! It's short-circuit now.
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