[GitHub] [arrow-datafusion] alamb commented on a change in pull request #291: Support Full Join

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alamb commented on a change in pull request #291:
URL: https://github.com/apache/arrow-datafusion/pull/291#discussion_r628874887



##########
File path: datafusion/src/physical_plan/hash_join.rs
##########
@@ -1515,6 +1589,43 @@ mod tests {
         Ok(())
     }
 
+    #[tokio::test]
+    async fn join_outer_one() -> Result<()> {
+        let left = build_table(
+            ("a1", &vec![1, 2, 3]),
+            ("b1", &vec![4, 5, 7]), // 7 does not exist on the right
+            ("c1", &vec![7, 8, 9]),
+        );
+        let right = build_table(
+            ("a2", &vec![10, 20, 30]),
+            ("b1", &vec![4, 5, 6]),
+            ("c2", &vec![70, 80, 90]),
+        );
+        let on = &[("b1", "b1")];
+
+        let join = join(left, right, on, &JoinType::Full)?;
+
+        let columns = columns(&join.schema());
+        assert_eq!(columns, vec!["a1", "b1", "c1", "a2", "c2"]);
+
+        let stream = join.execute(0).await?;
+        let batches = common::collect(stream).await?;
+
+        let expected = vec![
+            "+----+----+----+----+----+",
+            "| a1 | b1 | c1 | a2 | c2 |",
+            "+----+----+----+----+----+",
+            "|    |    |    | 30 | 90 |",

Review comment:
       this row should also have `b1=6` I think

##########
File path: ballista/rust/core/src/serde/physical_plan/to_proto.rs
##########
@@ -132,6 +132,7 @@ impl TryInto<protobuf::PhysicalPlanNode> for Arc<dyn 
ExecutionPlan> {
                 JoinType::Inner => protobuf::JoinType::Inner,
                 JoinType::Left => protobuf::JoinType::Left,
                 JoinType::Right => protobuf::JoinType::Right,
+                JoinType::Full => protobuf::JoinType::Right,

Review comment:
       This looks like it is a typo perhaps
   
   ```suggestion
                   JoinType::Full => protobuf::JoinType::Full,
   ```

##########
File path: datafusion/src/physical_plan/hash_join.rs
##########
@@ -1410,6 +1413,45 @@ mod tests {
         assert_batches_sorted_eq!(expected, &batches);
     }
 
+    #[tokio::test]
+    async fn join_outer_multi_batch() {
+        let left = build_table(
+            ("a1", &vec![1, 2, 3]),
+            ("b1", &vec![4, 5, 7]), // 7 does not exist on the right
+            ("c1", &vec![7, 8, 9]),
+        );
+        let right = build_table_two_batches(
+            ("a2", &vec![10, 20, 30]),
+            ("b1", &vec![4, 5, 6]),
+            ("c2", &vec![70, 80, 90]),
+        );
+        let on = &[("b1", "b1")];
+
+        let join = join(left, right, on, &JoinType::Full).unwrap();
+
+        let columns = columns(&join.schema());
+        assert_eq!(columns, vec!["a1", "b1", "c1", "a2", "c2"]);
+
+        let stream = join.execute(0).await.unwrap();
+        let batches = common::collect(stream).await.unwrap();
+
+        let expected = vec![

Review comment:
       This doesn't look like the correct answer to me. FULL OUTER JOIN 
basically keeps tuples from boths sides that don't match the join criteria.
   
   So we should have 2 rows for `b1=4' and `b1=5` and then 1 row for tuple on 
the left that has no match with the right, `b1=7` and 1 row for the tuple on 
the right that has no match with the left `b1=6`
   
   And indeed  postgres returns 4 rows as well
   
   
   ```
   alamb=# select * from tleft;
    a1 | b1 | c1 
   ----+----+----
     1 |  4 |  7
     2 |  5 |  8
     3 |  7 |  9
   (3 rows)
   
   alamb=# select * from tright;
    a2 | b2 | c2 
   ----+----+----
    10 |  4 | 70
     2 |  5 | 80
     3 |  6 | 90
   (3 rows)
   
   alamb=# select * from tleft FULL JOIN tright ON (tleft.b1 = tright.b2);
    a1 | b1 | c1 | a2 | b2 | c2 
   ----+----+----+----+----+----
     1 |  4 |  7 | 10 |  4 | 70
     2 |  5 |  8 |  2 |  5 | 80
       |    |    |  3 |  6 | 90
     3 |  7 |  9 |    |    |   
   (4 rows)
   ```




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