@Deprecated
  public static int getPdxRegistrySize() {
    InternalCache cache = GemFireCacheImpl.getExisting();
    TypeRegistry registry = cache.getPdxRegistry();
    if (registry == null) {
      return 0;
    }

    return registry.getLocalSize();
  }
adds a PdxType for a field to a {@code className => Set<PdxType>} map
geode-core/src/main/java/org/apache/geode/pdx/internal/PeerTypeRegistration.java