alamb commented on code in PR #4258:
URL: https://github.com/apache/arrow-datafusion/pull/4258#discussion_r1026837425
##########
datafusion/sql/src/planner.rs:
##########
@@ -3165,6 +3171,64 @@ fn wrap_projection_for_join_if_necessary(
Ok((plan, need_project))
}
+/// Ensure any column reference of the expression is determined.
Review Comment:
Another term for this concept is `unambiguous`
##########
datafusion/sql/src/planner.rs:
##########
@@ -3165,6 +3171,64 @@ fn wrap_projection_for_join_if_necessary(
Ok((plan, need_project))
}
+/// Ensure any column reference of the expression is determined.
+/// Assume we have two schema:
+/// schema1: a, b ,c
+/// schema2: a, d, e
+///
+/// `schema1.a + schema2.a` is determined.
+/// `a + d` is not determined, because `a` may come from schema1 or schema2.
+fn ensure_any_column_reference_is_determined(
+ expr: &Expr,
+ schemas: &[DFSchemaRef],
+) -> Result<()> {
+ if schemas.len() == 1 {
+ return Ok(());
+ }
+
+ // extract columns both in one more schemas.
+ let mut column_count_map: HashMap<String, usize> = HashMap::new();
Review Comment:
You might be able to avoid a clone into a string here. Maybe a follow on PR
```suggestion
let mut column_count_map: HashMap<&str, usize> = HashMap::new();
```
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