/** @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);
    }
  }
 /** @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());
 }