What does my partner do if I have a doula?
The short answer is, a lot!! You chose to be with them for a spesific reason, and as your doula I get it and respect it. Although he/she doesn't have the "birth" know-how, they do have the "you" know-how. Practically this translates in them holding your hand, rubbing your back, and being your rock.
What do I do then? I subtly remind them to do those things ;) I show them how to efficiently do a hip squeeze or hand them the warmed heat pack. Maybe you need to just want to hold on to them, but not give up on that blessed relief a back-rub brings; that's me! Sometimes both of you just need a reminder you are doing great, you can do this, and the end is in sight. Sometimes, if labour is long, the partner just needs a nap, but doesn't want to leave the mom alone. That's okay, I've got your back (literally as well, again, those hip squeezes are heavenly!).
With all seriousness though, in no way, shape of form do I replace your partner during labour and birth. Together we make your best support team. We bring different expertise to the labour that will benefit you immensely.