[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #2197: `case when` supports `NULL` constant

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

alamb commented on code in PR #2197:
URL: https://github.com/apache/arrow-datafusion/pull/2197#discussion_r849312085


##########
datafusion/physical-expr/src/expressions/case.rs:
##########
@@ -178,6 +178,13 @@ impl CaseExpr {
             let when_value = self.when_then_expr[i]
                 .0
                 .evaluate_selection(batch, &remainder)?;
+            // Treat 'NULL' as false value
+            let when_value = match when_value {
+                ColumnarValue::Scalar(value) if value.is_null() => {

Review Comment:
   This is a reasonable solution I think -- ideally we would have been able to coerce this value into a `ColumnarValue::Scalar(ScalarValue::Boolean(None))` at some earlier point.
   
   However, I think this special case is reasonable (and the test coverage is nice) so 👍  from me



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