/** @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);
    }
  }
  /** {@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();
    }
  }
 /** @throws GridException If query is invalid. */
 public void validate() throws GridException {
   if (type != SCAN && !cctx.config().isQueryIndexEnabled())
     throw new GridException("Indexing is disabled for cache: " + cctx.cache().name());
 }