[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #6799: fix: incorrect nullability of `InList` expr

["alamb (via GitHub)" <gi...@apache.org>]

alamb commented on code in PR #6799:
URL: https://github.com/apache/arrow-datafusion/pull/6799#discussion_r1246980465


##########
datafusion/expr/src/expr_schema.rs:
##########
@@ -173,8 +173,30 @@ impl ExprSchemable for Expr {
             Expr::Alias(expr, _)
             | Expr::Not(expr)
             | Expr::Negative(expr)
-            | Expr::Sort(Sort { expr, .. })
-            | Expr::InList(InList { expr, .. }) => expr.nullable(input_schema),
+            | Expr::Sort(Sort { expr, .. }) => expr.nullable(input_schema),
+
+            Expr::InList(InList { expr, list, .. }) => {
+                // Avoid inspecting too many expressions.
+                const MAX_INSPECT_LIMIT: usize = 6;
+                // Stop if a nullable expression is found or an error occurs.
+                let has_nullable = std::iter::once(expr.as_ref())
+                    .chain(list)
+                    .take(MAX_INSPECT_LIMIT)
+                    .find_map(|e| {
+                        e.nullable(input_schema)
+                            .map(|x| if x { Some(()) } else { None })

Review Comment:
   nit: I think calling this `nullable` would make the code easer to read:
   
   ```suggestion
                               .map(|nullable| if nullable { Some(()) } else { None })
   ```



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