Efficiency of public access vector

[Ganado]

In the following example class A is defined below, and class B is some unspecified type (if it makes a big difference what B is, please say so, for now just assume that's a sufficiently complicated type).

If I have something like

class A1 {
  public:
    const std::vector<B>& getV() const {return v;}
  private:
    std::vector<B> v;
};

vs.

class A2 {
  public:
    A() { /*populate v*/ }
    std::vector<B> v;
};

Will calling "a2_obj.v" make a copy of the each element (slow), or would it be like returning a reference like in the A1 class's accessor function a1_obj.getV() except it won't be const?