code: private Instance getExistingKey(final String _key)
      {
          Instance ret = null;
          try {
              final QueryBuilder queryBldr = new QueryBuilder(Type.get(DBPropertiesUpdate.TYPE_PROPERTIES));
              queryBldr.addWhereAttrEqValue("Key", _key);
              queryBldr.addWhereAttrEqValue("BundleID", this.bundleInstance);
              final InstanceQuery query = queryBldr.getQuery();
              query.executeWithoutAccessCheck();
              if (query.next()) {
                  ret = query.getCurrentValue();
              }
          } catch (final EFapsException e) {
              DBPropertiesUpdate.LOG.error("getExisting()", e);
          }
          return ret;
      }
docs: Is a key already existing.
  
  @param _key Key to search for
  @return OID of the key, otherwise null