/**
   * @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));
  }
  /** @return Nodes to execute on. */
  private Collection<GridNode> nodes() {
    GridCacheMode cacheMode = cctx.config().getCacheMode();

    switch (cacheMode) {
      case LOCAL:
        if (prj != null)
          U.warn(
              log,
              "Ignoring query projection because it's executed over LOCAL cache "
                  + "(only local node will be queried): "
                  + this);

        return Collections.singletonList(cctx.localNode());

      case REPLICATED:
        if (prj != null) return nodes(cctx, prj);

        GridCacheDistributionMode mode = cctx.config().getDistributionMode();

        return mode == PARTITIONED_ONLY || mode == NEAR_PARTITIONED
            ? Collections.singletonList(cctx.localNode())
            : Collections.singletonList(F.rand(nodes(cctx, null)));

      case PARTITIONED:
        return nodes(cctx, prj);

      default:
        throw new IllegalStateException("Unknown cache distribution mode: " + cacheMode);
    }
  }
  /**
   * Parses HTTP parameters in an appropriate format and return back map of values to predefined
   * list of names.
   *
   * @param req Request.
   * @return Map of parsed parameters.
   */
  @SuppressWarnings({"unchecked"})
  private Map<String, Object> parameters(ServletRequest req) {
    Map<String, String[]> params = req.getParameterMap();

    if (F.isEmpty(params)) return Collections.emptyMap();

    Map<String, Object> map = U.newHashMap(params.size());

    for (Map.Entry<String, String[]> entry : params.entrySet())
      map.put(entry.getKey(), parameter(entry.getValue()));

    return map;
  }
  /**
   * @param cctx Cache context.
   * @param prj Projection (optional).
   * @return Collection of data nodes in provided projection (if any).
   */
  private static Collection<GridNode> nodes(
      final GridCacheContext<?, ?> cctx, @Nullable final GridProjection prj) {
    assert cctx != null;

    return F.view(
        CU.allNodes(cctx),
        new P1<GridNode>() {
          @Override
          public boolean apply(GridNode n) {
            GridCacheDistributionMode mode = U.distributionMode(n, cctx.name());

            return (mode == PARTITIONED_ONLY || mode == NEAR_PARTITIONED)
                && (prj == null || prj.node(n.id()) != null);
          }
        });
  }