for ( java.util.Iterator it = expressions.iterator(); it.hasNext(); )
                {
                    Expression expr = (Expression) it.next();

                    expressionsBySyntax.put( expr.getSyntax(), expr );
                }
            }
        }

        return expressionsBySyntax;
    }

    public void flushExpressionsBySyntax()
    {
        expressionsBySyntax = null;
    }