Is there a working example of the Quarkus Cassandra Client for Pagination?

With the latest cassandra bom you can run those tests

<dependency>
    <groupId>com.datastax.oss.quarkus</groupId>
    <artifactId>cassandra-quarkus-bom</artifactId>
    <version>1.1.2</version>
    <type>pom</type>
    <scope>import</scope>
</dependency>

with that docker cassandra started working, after that your function started working

    @Override
    public List<Customer> findPagedCustomerByCustomerNumber(String customerNumber, int pageNumber, int pageSize) {
        List<Customer> result = new ArrayList<>();
        PreparedStatement query = cqlSession.prepare(
                "SELECT * FROM test.customer WHERE customer_number = :customerNumber ORDER BY  creation_date");
        BoundStatement completeStatement = query.bind().setString("customerNumber", customerNumber);
        OffsetPager pager = new OffsetPager(pageSize);
        ResultSet resultSet = cqlSession.execute(completeStatement);
        OffsetPager.Page<Row> page = pager.getPage(resultSet, pageNumber);
        List<Row> pageElements = page.getElements();
        pageElements.forEach(c -> result.add(Customer.builder()
                .customerNumber(c.getString("customer_number"))
                .creationDate(c.getLocalDate("creation_date"))
                .description(c.getString("description"))
                .state(c.getString("state"))
                .build())
        );
        return result;
    }

I have been using querybuilder for a long time so I added that too

public List<Customer> findPagedCustomerByCustomerNumberPaging(String customerNumber, int pageNumber, int pageSize) {
        List<Customer> result = new ArrayList<>();
        Select select = QueryBuilder.selectFrom("test", "customer")
                .columns("customer_number", "creation_date", "description", "state")
                .whereColumn("customer_number").isEqualTo(literal(customerNumber))
                .orderBy("createtion_date", ClusteringOrder.ASC)
                .allowFiltering();

        SimpleStatement completeStatement = select.build();
        OffsetPager pager = new OffsetPager(pageSize);
        ResultSet resultSet = cqlSession.execute(completeStatement);
        OffsetPager.Page<Row> page = pager.getPage(resultSet, pageNumber);
        List<Row> pageElements = page.getElements();
        pageElements.forEach(c -> result.add(Customer.builder()
                .customerNumber(c.getString("customer_number"))
                .creationDate(c.getLocalDate("creation_date"))
                .description(c.getString("description"))
                .state(c.getString("state"))
                .build())
        );
        return result;
    }

I understand cassandra-quarkus-test-framework brings docker but in case you dont have docker you can always use CassandraUnit which is lighter then docker. All code can be found here.

There is pagination in the Quarkus Cassandra client however I can't make it work as I would like either. Below you see an example to get the pagination state with the example from the quarkus documentation https://quarkus.io/guides/cassandra

public PagingFruit getPagingState(String pagingState){
        ByteBuffer state = ByteBuffer.wrap(pagingState.getBytes());
        MutinyMappedReactiveResultSet<Fruit> fruit = this.fruitMapper.fruitDao().findAll(x -> x.setPagingState(state).setPageSize(1000); // here we provide the unary operator that sets the state.  
        var newState = Uni.createFrom().publisher(fruit.getExecutionInfos()).map(ExecutionInfo::getPagingState).await().indefinitely().toString();
        return new PagingFruit(fruit.collect().asList().await().indefinitely(), newState);
}

record PagingFruit(List<Fruit> fruit, String pagingState){}

This uses the MutinyMappedReactiveResultSet which allows you to query the ExecutionInfos.

The problem I have at this moment using the quarkus implementation is that I need to query Cassandra twice to actually provide the data and the pagination with it. Therefore I opted for a prepared statement like this example:

class PaginatedRepository {

    private final QuarkusCqlSession cqlSession;
    private final PreparedStatement query;
    
    PaginatedRepository(QuarkusCqlSession quarkusCqlSession){
        this.cqlSession = quarkusCqlSession;
        this.query = cqlSession.prepare("SELECT fruit FROM keypace.table");
    }
    
    public Uni<PagingFruit> findFruit(String page) {
        var statement = query
                .bind()
                .setPageSize(1000)
                .setPagingState(PagingState.fromString(page));
    
        return Uni.createFrom().completionStage(cqlSession.executeAsync(statement))
                .map(resultSet -> {
                    var pagingState = resultSet.getExecutionInfo().getSafePagingState();
                    var newCursor = (pagingState == null) ? null : pagingState.toString();
                    var rows = Streams.stream(resultSet.currentPage())
                            .map(row -> row.get(1, Fruit.class)
                            ).filter(Objects::nonNull).toList();
                    return new PagingFruit(rows, newCursor);
                });
    }

This is untested code, just the general concept which should work.

So, in my oppinion and my research, there is no convinient way to do pagination on a cassandra database with the quarkus cassandra client. You have to handle it by yourself.