[GitHub] [arrow] alamb commented on a change in pull request #9116: ARROW-11156: [Rust][DataFusion] Create hashes vectorized in hash join

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

alamb commented on a change in pull request #9116:
URL: https://github.com/apache/arrow/pull/9116#discussion_r558531603



##########
File path: rust/datafusion/src/physical_plan/hash_join.rs
##########
@@ -936,4 +1096,53 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn join_with_hash_collision() -> Result<()> {
+        let mut hashmap_left = HashMap::with_hasher(IdHashBuilder {});
+        let left = build_table_i32(
+            ("a", &vec![10, 20]),
+            ("x", &vec![100, 200]),
+            ("y", &vec![200, 300]),
+        );
+
+        let random_state = RandomState::new();
+
+        let hashes = create_hashes(&[left.columns()[0].clone()], &random_state)?;
+
+        // Create hash collisions
+        hashmap_left.insert(hashes[0], vec![0, 1]);
+        hashmap_left.insert(hashes[1], vec![0, 1]);
+
+        let right = build_table_i32(
+            ("a", &vec![10, 20]),
+            ("b", &vec![0, 0]),
+            ("c", &vec![30, 40]),
+        );
+
+        let left_data = JoinLeftData::new((hashmap_left, left));
+        let (l, r) = build_join_indexes(
+            &left_data,
+            &right,
+            JoinType::Inner,

Review comment:
       I recommend adding a test that covers collisions for all the `JoinType` variants -- the path for collision handling is different for those different join type variants. 




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