core/src/main/java/com/orientechnologies/orient/core/db/record/ridbag/ORidBag.java
public boolean tryMerge(final ORidBag otherValue, boolean iMergeSingleItemsOfMultiValueFields) {
    if (!isEmbedded() && !otherValue.isEmbedded()) {
      final OSBTreeRidBag thisTree = (OSBTreeRidBag) delegate;
      final OSBTreeRidBag otherTree = (OSBTreeRidBag) otherValue.delegate;
      if (thisTree.getCollectionPointer().equals(otherTree.getCollectionPointer())) {

        thisTree.mergeChanges(otherTree);

        uuid = otherValue.uuid;

        return true;
      }
    } else if (iMergeSingleItemsOfMultiValueFields) {
      final Iterator<OIdentifiable> iter = otherValue.rawIterator();
      while (iter.hasNext()) {
        final OIdentifiable value = iter.next();
        if (value != null) {
          final Iterator<OIdentifiable> localIter = rawIterator();
          boolean found = false;
          while (localIter.hasNext()) {
            final OIdentifiable v = localIter.next();
            if (value.equals(v)) {
              found = true;
              break;
            }
          }
          if (!found)
            add(value);
        }
      }
      return true;
    }
    return false;
  }
public boolean tryMerge(final ORidBag otherValue, boolean iMergeSingleItemsOfMultiValueFields) {
    if (!isEmbedded() && !otherValue.isEmbedded()) {
      final OSBTreeRidBag thisTree = (OSBTreeRidBag) delegate;
      final OSBTreeRidBag otherTree = (OSBTreeRidBag) otherValue.delegate;
      if (thisTree.getCollectionPointer().equals(otherTree.getCollectionPointer())) {

        thisTree.mergeChanges(otherTree);

        uuid = otherValue.uuid;

        return true;
      }
    } else if (iMergeSingleItemsOfMultiValueFields) {
      final Iterator<OIdentifiable> iter = otherValue.rawIterator();
      while (iter.hasNext()) {
        final OIdentifiable value = iter.next();
        if (value != null) {
          final Iterator<OIdentifiable> localIter = rawIterator();
          boolean found = false;
          while (localIter.hasNext()) {
            final OIdentifiable v = localIter.next();
            if (value.equals(v)) {
              found = true;
              break;
            }
          }
          if (!found)
            add(value);
        }
      }
      return true;
    }
    return false;
  }
IMPORTANT! Only for internal usage.