/**
   * Checks that gets work for implicit txs.
   *
   * @param cache Cache to test.
   * @throws Exception If failed.
   */
  private void checkExplicitTx(Ignite ignite, IgniteCache<String, String> cache) throws Exception {
    IgniteCache<String, String> asyncCache = cache.withAsync();

    Transaction tx = ignite.transactions().txStart();

    try {
      assertNull(cache.get("key1"));

      tx.commit();
    } finally {
      tx.close();
    }

    tx = ignite.transactions().txStart();

    try {
      asyncCache.get("key2");

      assertNull(asyncCache.future().get());

      tx.commit();
    } finally {
      tx.close();
    }

    tx = ignite.transactions().txStart();

    try {
      assertTrue(cache.getAll(F.asSet("key3", "key4")).isEmpty());

      tx.commit();
    } finally {
      tx.close();
    }

    tx = ignite.transactions().txStart();

    try {
      asyncCache.getAll(F.asSet("key5", "key6"));

      assertTrue(((Map) asyncCache.future().get()).isEmpty());

      tx.commit();
    } finally {
      tx.close();
    }

    tx = ignite.transactions().txStart();

    try {
      cache.put("key7", "key7");

      cache.remove("key7");

      assertNull(cache.get("key7"));

      tx.commit();
    } finally {
      tx.close();
    }

    checkEmpty(cache);
  }
    /** @param nodes Nodes. */
    private Queue<ClusterNode> fallbacks(Collection<ClusterNode> nodes) {
      Queue<ClusterNode> fallbacks = new LinkedList<>();

      ClusterNode node = F.first(F.view(nodes, IS_LOC_NODE));

      if (node != null) fallbacks.add(node);

      fallbacks.addAll(node != null ? F.view(nodes, F.not(IS_LOC_NODE)) : nodes);

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

    final AffinityTopologyVersion topVer = cctx.affinity().affinityTopologyVersion();

    Collection<ClusterNode> affNodes = CU.affinityNodes(cctx);

    if (prj == null && part == null) return affNodes;

    final Set<ClusterNode> owners =
        part == null
            ? Collections.<ClusterNode>emptySet()
            : new HashSet<>(cctx.topology().owners(part, topVer));

    return F.view(
        affNodes,
        new P1<ClusterNode>() {
          @Override
          public boolean apply(ClusterNode n) {

            return cctx.discovery().cacheAffinityNode(n, cctx.name())
                && (prj == null || prj.node(n.id()) != null)
                && (part == null || owners.contains(n));
          }
        });
  }
  /** @return Nodes to execute on. */
  private Collection<ClusterNode> nodes() {
    CacheMode 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 || partition() != null) return nodes(cctx, prj, partition());

        return cctx.affinityNode()
            ? Collections.singletonList(cctx.localNode())
            : Collections.singletonList(F.rand(nodes(cctx, null, partition())));

      case PARTITIONED:
        return nodes(cctx, prj, partition());

      default:
        throw new IllegalStateException("Unknown cache distribution mode: " + cacheMode);
    }
  }
  /**
   * Checks that gets work for implicit txs.
   *
   * @param cache Cache to test.
   * @throws Exception If failed.
   */
  private void checkImplicitTx(IgniteCache<String, String> cache) throws Exception {
    assertNull(cache.get("key1"));

    IgniteCache<String, String> asyncCache = cache.withAsync();

    asyncCache.get("key2");

    assertNull(asyncCache.future().get());

    assertTrue(cache.getAll(F.asSet("key3", "key4")).isEmpty());

    asyncCache.getAll(F.asSet("key5", "key6"));

    assertTrue(((Map) asyncCache.future().get()).isEmpty());

    cache.put("key7", "key7");
    cache.remove("key7", "key7");
    assertNull(cache.get("key7"));

    checkEmpty(cache);
  }
  /**
   * @param rmtReducer Optional reducer.
   * @param rmtTransform Optional transformer.
   * @param args Arguments.
   * @return Future.
   */
  @SuppressWarnings("IfMayBeConditional")
  private <R> CacheQueryFuture<R> execute(
      @Nullable IgniteReducer<T, R> rmtReducer,
      @Nullable IgniteClosure<T, R> rmtTransform,
      @Nullable Object... args) {
    Collection<ClusterNode> nodes = nodes();

    cctx.checkSecurity(SecurityPermission.CACHE_READ);

    if (nodes.isEmpty())
      return new GridCacheQueryErrorFuture<>(
          cctx.kernalContext(), new ClusterGroupEmptyCheckedException());

    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 (IgniteCheckedException e) {
        return new GridCacheQueryErrorFuture<>(cctx.kernalContext(), e);
      }
    }

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

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

    final GridCacheQueryBean bean =
        new GridCacheQueryBean(
            this,
            (IgniteReducer<Object, Object>) rmtReducer,
            (IgniteClosure<Object, Object>) rmtTransform,
            args);

    final GridCacheQueryManager qryMgr = cctx.queries();

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

    if (type == SQL_FIELDS || type == SPI)
      return (CacheQueryFuture<R>)
          (loc ? qryMgr.queryFieldsLocal(bean) : qryMgr.queryFieldsDistributed(bean, nodes));
    else if (type == SCAN && part != null && nodes.size() > 1)
      return new CacheQueryFallbackFuture<>(nodes, bean, qryMgr);
    else
      return (CacheQueryFuture<R>)
          (loc ? qryMgr.queryLocal(bean) : qryMgr.queryDistributed(bean, nodes));
  }
  /** @throws Exception If failed. */
  public void testGroupIndexOperations() throws Exception {
    IgniteCache<Integer, GroupIndexTestValue> c =
        ignite(0)
            .getOrCreateCache(cacheConfig("grp", false, Integer.class, GroupIndexTestValue.class));

    try {
      // Check group index usage.
      String qry = "select 1 from GroupIndexTestValue ";

      String plan = columnQuery(c, "explain " + qry + "where a = 1 and b > 0").get(0).toString();

      info("Plan: " + plan);

      assertTrue(plan.contains("grpIdx"));

      // Sorted list
      List<GroupIndexTestValue> list =
          F.asList(
              new GroupIndexTestValue(0, 0),
              new GroupIndexTestValue(0, 5),
              new GroupIndexTestValue(1, 1),
              new GroupIndexTestValue(1, 3),
              new GroupIndexTestValue(2, -1),
              new GroupIndexTestValue(2, 2));

      // Fill cache.
      for (int i = 0; i < list.size(); i++) c.put(i, list.get(i));

      // Check results.
      assertEquals(1, columnQuery(c, qry + "where a = 1 and b = 1").size());
      assertEquals(2, columnQuery(c, qry + "where a = 1 and b < 4").size());
      assertEquals(2, columnQuery(c, qry + "where a = 1 and b <= 3").size());
      assertEquals(1, columnQuery(c, qry + "where a = 1 and b < 3").size());
      assertEquals(2, columnQuery(c, qry + "where a = 1 and b > 0").size());
      assertEquals(1, columnQuery(c, qry + "where a = 1 and b > 1").size());
      assertEquals(2, columnQuery(c, qry + "where a = 1 and b >= 1").size());
      assertEquals(4, columnQuery(c, qry + "where a > 0 and b > 0").size());
      assertEquals(4, columnQuery(c, qry + "where a > 0 and b >= 1").size());
      assertEquals(3, columnQuery(c, qry + "where a > 0 and b > 1").size());
    } finally {
      c.destroy();
    }
  }