integration: add regression test for shorter tuples

After #1452 is fixed in a previous commit, now we add a regression test
to ensure that tuples encoded with fewer elements than in the metadata
are accepted and decoded correctly (missing elements are returned as
null). The test would fail before the fix.

Co-authored-by: Karol Baryła <[email protected]>

Author: wprzytula

scylla/tests/integration/types/cql_collections.rs

@@ -254,6 +254,55 @@ async fn test_cql_tuple() {
         .unwrap();
 }
 
+// Cassandra does not support altering column types starting with version 3.0.11 and 3.10.
+// See https://stackoverflow.com/a/76926622 for explanation.
+#[cfg_attr(cassandra_tests, ignore)]
+#[tokio::test]
+async fn test_alter_column_add_field_to_tuple() {
+    setup_tracing();
+    let session: Session = connect().await;
+
+    let table_name: &str = "test_cql_tuple_alter_tab";
+    create_table(&session, table_name, "tuple<int, int>").await;
+
+    let tuple1: (i32, i32) = (1, 2);
+    session
+        .query_unpaged(
+            format!("INSERT INTO {table_name} (p, val) VALUES (0, ?)"),
+            &(tuple1,),
+        )
+        .await
+        .unwrap();
+
+    // Add a field to the tuple. Existing rows will still have 2 fields in the tuple.
+    session
+        .query_unpaged(
+            format!("ALTER TABLE {table_name} ALTER val TYPE tuple<int, int, text>"),
+            &(),
+        )
+        .await
+        .unwrap();
+
+    // Select a tuple - ScyllaDB will send 2-element tuple.
+    // Driver should return the third element as null.
+    let selected_value: (Option<i32>, Option<i32>, Option<String>) = session
+        .query_unpaged(format!("SELECT val FROM {table_name} WHERE p = 0"), ())
+        .await
+        .unwrap()
+        .into_rows_result()
+        .unwrap()
+        .single_row::<((Option<i32>, Option<i32>, Option<String>),)>()
+        .unwrap()
+        .0;
+
+    assert!(selected_value.2.is_none());
+
+    session
+        .ddl(format!("DROP KEYSPACE {}", session.get_keyspace().unwrap()))
+        .await
+        .unwrap();
+}
+
 // TODO: Remove this ignore when vector type is supported in ScyllaDB
 #[cfg_attr(not(cassandra_tests), ignore)]
 #[tokio::test]