feat: add +1 to rowaffected in upsert engine only if update returns a…

… rowaffected value, added e2e test for multiple rows

Signed-off-by: Harshit Gangal <harshit@planetscale.com>

go/test/endtoend/vtgate/foreignkey/fk_test.go

@@ -1232,4 +1232,9 @@ func TestInsertWithFKOnDup(t *testing.T) {
 	mcmp.Exec(`insert into u_t1(id, col1) values (100, 75) on duplicate key update col1 = values(col1)`)
 	mcmp.AssertMatches(`select * from u_t1 order by id`, `[[INT64(100) INT64(75)] [INT64(200) INT64(2)] [INT64(300) INT64(3)] [INT64(400) INT64(50)]]`)
 	mcmp.AssertMatches(`select * from u_t2 order by id`, `[[INT64(1000) NULL] [INT64(2000) INT64(2)] [INT64(3000) INT64(3)] [INT64(4000) NULL]]`)
+
+	// inserting multiple rows in parent, some child rows updated to null.
+	mcmp.Exec(`insert into u_t1(id, col1) values (100, 42),(600, 2),(300, 24),(200, 2) on duplicate key update col1 = values(col1)`)
+	mcmp.AssertMatches(`select * from u_t1 order by id`, `[[INT64(100) INT64(42)] [INT64(200) INT64(2)] [INT64(300) INT64(24)] [INT64(400) INT64(50)] [INT64(600) INT64(2)]]`)
+	mcmp.AssertMatches(`select * from u_t2 order by id`, `[[INT64(1000) NULL] [INT64(2000) INT64(2)] [INT64(3000) NULL] [INT64(4000) NULL]]`)
 }

go/vt/vtgate/engine/upsert.go

@@ -101,8 +101,10 @@ func execOne(ctx context.Context, vcursor VCursor, bindVars map[string]*querypb.
 	if err != nil {
 		return nil, err
 	}
-	// To match mysql, need to report +1 on rows affected.
-	updQr.RowsAffected += 1
+	// To match mysql, need to report +1 on rows affected if there is any change.
+	if updQr.RowsAffected > 0 {
+		updQr.RowsAffected += 1
+	}
 	return updQr, nil
 }