[GitHub] [arrow-datafusion] Jimexist commented on a change in pull request #605: fix join column handling logic for `On` and `Using` constraints

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

Jimexist commented on a change in pull request #605:
URL: https://github.com/apache/arrow-datafusion/pull/605#discussion_r664538972



##########
File path: datafusion/src/logical_plan/dfschema.rs
##########
@@ -149,47 +147,80 @@ impl DFSchema {
         )))
     }
 
-    /// Find the index of the column with the given qualifer and name
-    pub fn index_of_column(&self, col: &Column) -> Result<usize> {
-        for i in 0..self.fields.len() {
-            let field = &self.fields[i];
-            if field.qualifier() == col.relation.as_ref() && field.name() == &col.name {
-                return Ok(i);
-            }
+    fn index_of_column_by_name(
+        &self,
+        qualifier: Option<&str>,
+        name: &str,
+    ) -> Result<usize> {
+        let matches: Vec<usize> = self
+            .fields
+            .iter()
+            .enumerate()
+            .filter(|(_, field)| match (qualifier, &field.qualifier) {
+                // field to lookup is qualified.
+                // current field is qualified and not shared between relations, compare both
+                // qualifer and name.
+                (Some(q), Some(field_q)) => q == field_q && field.name() == name,
+                // field to lookup is qualified but current field is unqualified.
+                (Some(_), None) => false,
+                // field to lookup is unqualified, no need to compare qualifier
+                _ => field.name() == name,

Review comment:
       prefer to write out cases, `(None, None)` and `(None, Some(_)` and union them. this makes it clearer?




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