phillipleblanc opened a new issue, #16147:
URL: https://github.com/apache/datafusion/issues/16147
### Describe the bug
The TreeNode implementation for `Expr` does not handle the
`outer_ref_column` expressions present in the `Subquery` nodes of
`Expr::InSubquery`, `Expr::ScalarSubquery`, and `Expr::Exists`.
The LogicalPlan::map_expressions implementation does not handle the
`outer_ref_column` expression in `LogicalPlan::Subquery`
### To Reproduce
Create a LogicalPlan from a SQL statement with a subquery expression that
has an outer column reference, i.e.
```
SELECT
e.employee_id,
e.first_name,
e.salary
FROM
employees e
WHERE
e.salary > (
SELECT AVG(salary)
FROM employees e2
WHERE e2.department_id = e.department_id
);
```
I would expect to be able to do something like this:
```rust
let plan = sql_to_plan(sql);
plan.apply(|plan| {
plan.apply_expressions(|expr| {
match expr {
Expr::OuterReferenceColumn(_, _) => { do something useful }
_ => Ok(Transformed::no(expr))
}
});
});
```
### Expected behavior
The `outer_ref_column` expressions are part of the TreeNode visitor
implementations in both Expr and LogicalPlan
### Additional context
I will not work on this, so someone should feel free to take this. There is
a workaround if you know about this behavior, which is to match on the
expressions/plans which contain these outer ref column expressions.
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