code: @Nonnull
    public final <T> JPAExecutionResult <T> doSelect (@Nonnull final Callable <T> aCallable)
    {
      if (isUseTransactionsForSelect ())
      {
        // Use transactions for select statement!
        return doInTransaction (aCallable);
      }
  
      // Ensure that only one transaction is active for all users!
      final EntityManager aEntityMgr = getEntityManager ();
      if (!isSyncEntityMgr ())
      {
        // No synchronization required
        return doSelectStatic (aCallable);
      }
  
      // Sync on the whole entity manager, to have a cross-manager
      // synchronization!
      synchronized (aEntityMgr)
      {
        return doSelectStatic (aCallable);
      }
    }
docs: Run a read-only query. By default no transaction is used, and the entity
  manager is synchronized.
  
  @param aCallable
  The callable to execute.
  @return A non-<code>null</code> result of the select.
  @param <T>
  Return type of the callable