cql: fix lists::setter to use a tombstone

Properly squash existing value

cql3/lists.hh

@@ -328,16 +328,12 @@ public:
         }
 
         virtual void execute(mutation& m, const exploded_clustering_prefix& prefix, const update_parameters& params) override {
+            tombstone ts;
             if (column.type->is_multi_cell()) {
                 // delete + append
-                // FIXME:
-                warn(unimplemented::cause::COLLECTIONS);
-#if 0
-                CellName name = cf.getComparator().create(prefix, column);
-                cf.addAtom(params.makeTombstoneForOverwrite(name.slice()));
-#endif
+                ts = params.make_tombstone_just_before();
             }
-            do_append(_t, m, prefix, column, params);
+            do_append(_t, m, prefix, column, params, ts);
         }
     };
 
@@ -418,7 +414,8 @@ public:
             mutation& m,
             const exploded_clustering_prefix& prefix,
             const column_definition& column,
-            const update_parameters& params) {
+            const update_parameters& params,
+            tombstone ts = {}) {
         auto&& value = t->bind(params._options);
         auto&& list_value = dynamic_pointer_cast<lists::value>(value);
         auto&& ltype = dynamic_pointer_cast<list_type_impl>(column.type);
@@ -431,6 +428,7 @@ public:
 
             auto&& to_add = list_value->_elements;
             collection_type_impl::mutation appended;
+            appended.tomb = ts;
             appended.cells.reserve(to_add.size());
             for (auto&& e : to_add) {
                 auto uuid1 = utils::UUID_gen::get_time_UUID_bytes();

tests/urchin/cql_query_test.cc

@@ -501,11 +501,8 @@ SEASTAR_TEST_CASE(test_list_insert_update) {
     }).then([state, db] {
         return state->execute_cql("update cf set list1 = [ 1002, 1003 ] where p1 = 'key1';").discard_result();
     }).then([state, db] {
-#if 0
-        // test fails due to lack of collection tombstones (append instead of replace)
         return require_column_has_value(*db, ks_name, table_name, {sstring("key1")}, {},
                 "list1", list_type_impl::native_type({boost::any(1002), boost::any(1003)}));
-#endif
     }).then([db] {
         return db->stop();
     }).then_wrapped([db] (future<> f) mutable {