/**
   * @param rmtReducer Optional reducer.
   * @param rmtTransform Optional transformer.
   * @param args Arguments.
   * @return Future.
   */
  @SuppressWarnings("IfMayBeConditional")
  private <R> GridCacheQueryFuture<R> execute(
      @Nullable GridReducer<T, R> rmtReducer,
      @Nullable GridClosure<T, R> rmtTransform,
      @Nullable Object... args) {
    Collection<GridNode> nodes = nodes();

    cctx.checkSecurity(GridSecurityPermission.CACHE_READ);

    if (F.isEmpty(nodes))
      return new GridCacheQueryErrorFuture<>(
          cctx.kernalContext(),
          new GridEmptyProjectionException("There are no data nodes for cache: " + cctx.namexx()));

    if (log.isDebugEnabled())
      log.debug("Executing query [query=" + this + ", nodes=" + nodes + ']');

    if (cctx.deploymentEnabled()) {
      try {
        cctx.deploy().registerClasses(filter, rmtReducer, rmtTransform);
        cctx.deploy().registerClasses(args);
      } catch (GridException e) {
        return new GridCacheQueryErrorFuture<>(cctx.kernalContext(), e);
      }
    }

    if (subjId == null) subjId = cctx.localNodeId();

    taskHash = cctx.kernalContext().job().currentTaskNameHash();

    GridCacheQueryBean bean =
        new GridCacheQueryBean(
            this,
            (GridReducer<Object, Object>) rmtReducer,
            (GridClosure<Object, Object>) rmtTransform,
            args);

    GridCacheQueryManager qryMgr = cctx.queries();

    boolean loc = nodes.size() == 1 && F.first(nodes).id().equals(cctx.localNodeId());

    if (type == SQL_FIELDS)
      return (GridCacheQueryFuture<R>)
          (loc ? qryMgr.queryFieldsLocal(bean) : qryMgr.queryFieldsDistributed(bean, nodes));
    else
      return (GridCacheQueryFuture<R>)
          (loc ? qryMgr.queryLocal(bean) : qryMgr.queryDistributed(bean, nodes));
  }
  /** {@inheritDoc} */
  @Override
  public void execute(@Nullable GridProjection prj) throws GridException {
    if (cb == null)
      throw new IllegalStateException("Mandatory local callback is not set for the query: " + this);

    if (prj == null) prj = ctx.grid();

    prj = prj.forCache(ctx.name());

    if (prj.nodes().isEmpty())
      throw new GridTopologyException("Failed to execute query (projection is empty): " + this);

    GridCacheMode mode = ctx.config().getCacheMode();

    if (mode == LOCAL || mode == REPLICATED) {
      Collection<GridNode> nodes = prj.nodes();

      GridNode node = nodes.contains(ctx.localNode()) ? ctx.localNode() : F.rand(nodes);

      assert node != null;

      if (nodes.size() > 1 && !ctx.cache().isDrSystemCache()) {
        if (node.id().equals(ctx.localNodeId()))
          U.warn(
              log,
              "Continuous query for "
                  + mode
                  + " cache can be run only on local node. "
                  + "Will execute query locally: "
                  + this);
        else
          U.warn(
              log,
              "Continuous query for "
                  + mode
                  + " cache can be run only on single node. "
                  + "Will execute query on remote node [qry="
                  + this
                  + ", node="
                  + node
                  + ']');
      }

      prj = prj.forNode(node);
    }

    closeLock.lock();

    try {
      if (routineId != null)
        throw new IllegalStateException("Continuous query can't be executed twice.");

      guard.block();

      GridContinuousHandler hnd =
          new GridCacheContinuousQueryHandler<>(ctx.name(), topic, cb, filter, prjPred);

      routineId =
          ctx.kernalContext()
              .continuous()
              .startRoutine(hnd, bufSize, timeInterval, autoUnsubscribe, prj.predicate())
              .get();
    } finally {
      closeLock.unlock();
    }
  }