如何在工作线程上执行vertx-jdbc-client查询？

Question

我正在使用vertx-jdbc-client查询数据库。我使用了subscriptionOn（scheduler）并期望以下查询在工作线程中执行，但是它似乎在事件循环线程上执行。

如何使该查询在工作线程上执行？

    import io.reactivex.Observable;
    import io.reactivex.Scheduler;
    import io.vertx.reactivex.core.AbstractVerticle;
    import io.vertx.core.Future;
    import io.vertx.core.json.JsonObject;
    import io.vertx.reactivex.ext.jdbc.JDBCClient;
    import io.vertx.reactivex.core.RxHelper;

    public class TestVerticle extends AbstractVerticle {

        JDBCClient jdbc;

        @Override
        public void start(Future<Void> fut) {

            jdbc = JDBCClient.createNonShared(vertx,
                    new JsonObject().put("url", "jdbc:hsqldb:mem:test?shutdown=true")
                            .put("driver_class", "org.hsqldb.jdbcDriver")
                            .put("max_pool_size", 3));

            fut.complete();

            //vertx.setPeriodic(5000, id -> {
            //  test();
            //});
            test();
        }

        public void test() {

            Scheduler scheduler = RxHelper.blockingScheduler(vertx);

            jdbc.rxGetConnection()
            .subscribeOn(scheduler)
            .flatMap(conn -> {
                Thread.sleep(3000); //Vertx BlockedThreadChecker prints warning if this is on event loop thread.
                return conn.rxQuery("select 42 from (values(0))")
                        .doAfterTerminate(conn::close);
            })
            .subscribe(rs -> {
                System.out.println(rs.getRows().toString() + " " + Thread.currentThread().getName());
            });

            //Check subscribeOn(scheduler) really works on worker thread if jdbc-client is not used.
            Observable.range(1, 1).subscribeOn(scheduler).subscribe(i -> {
                Thread.sleep(3000); //Vertx BlockedThreadChecker prints warning if this is on event loop thread.
                System.out.println(i + " " + Thread.currentThread().getName());
            });
        }

    }

输出：

1 vert.x-worker-thread-3
io.vertx.core.impl.BlockedThreadChecker
WARNING: Thread Thread[vert.x-eventloop-thread-2,5,main] has been blocked for 2747 ms, time limit is 2000 ms
[{"C1":42}] vert.x-eventloop-thread-2