[GitHub] [arrow-datafusion] alamb commented on a change in pull request #1601: fix: casting Int64 to Float64 unsuccessfully caused tpch8 to fail

[GitBox <gi...@apache.org>]

alamb commented on a change in pull request #1601:
URL: https://github.com/apache/arrow-datafusion/pull/1601#discussion_r786905414



##########
File path: datafusion/src/physical_plan/expressions/case.rs
##########
@@ -324,7 +325,10 @@ impl CaseExpr {
 
         // start with the else condition, or nulls
         let mut current_value: Option<ArrayRef> = if let Some(e) = &self.else_expr {
-            Some(e.evaluate(batch)?.into_array(batch.num_rows()))
+            // keep `else_expr`'s data type and return type consistent

Review comment:
       Eventually it would be great to separate out the `coercion` logic into the `
   
   ```rust
   
   /// Create a CASE expression
   pub fn case(
       expr: Option<Arc<dyn PhysicalExpr>>,
       when_thens: &[WhenThen],
       else_expr: Option<Arc<dyn PhysicalExpr>>,
   ) -> Result<Arc<dyn PhysicalExpr>> {
       Ok(Arc::new(CaseExpr::try_new(expr, when_thens, else_expr)?))
   }
   
   ```
   
   function the way it is done with `BinaryExpr` and `binary_cast`
   
   https://github.com/apache/arrow-datafusion/blob/master/datafusion/src/physical_plan/expressions/binary.rs#L1106-L1114
   
   But this is better than master so 👍 




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