[GitHub] [arrow-datafusion] yjshen commented on a change in pull request #2068: Short-circuit evaluation for `CaseWhen`

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

yjshen commented on a change in pull request #2068:
URL: https://github.com/apache/arrow-datafusion/pull/2068#discussion_r833077973



##########
File path: datafusion-physical-expr/src/expressions/case.rs
##########
@@ -523,6 +528,39 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn case_with_expr_divide_by_zero() -> Result<()> {
+        let batch = case_test_batch1()?;
+        let schema = batch.schema();
+
+        // CASE a when 0 THEN float64(null) ELSE 25.0 / cast(a, float64)  END
+        let when1 = lit(ScalarValue::Int32(Some(0)));

Review comment:
       Also, we are evaluating `case_when` from the end to the beginning. This is problematic since **short-circuit evaluation** is adopted by most engines, including PostgreSQL, Oracle, and SQL Server. Therefore, chances are users would express computation logic that would fail in later `when_thens` for tuples that **should have been** computed previously and bypassed.




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