presto-memory/src/main/java/io/prestosql/plugin/memory/MemoryPageSinkProvider.java/MemoryPageSink/finish
class MemoryPageSink:        @Override
        public CompletableFuture<Collection<Slice>> finish()
        {
            return completedFuture(ImmutableList.of(new MemoryDataFragment(currentHostAddress, addedRows).toSlice()));
        }