solid state physics - How holes conduct current?

I had questions about holes in semiconductor, when i checked the net it is said holes are said to be equivalent positive charge and they say because the hole moves from one place to another when it is occupied by electron the electron leaves holes and etc... But i couldn't find the clear answer in " P type " semi conductor it is written the holes in the valence band increase, my problem is i see that lags and reduces the current not increases it because the holes somehow will attract electrons and get them from conduction band to valence band and since the conduction band is the band that does current , isn't that will reduce current not increase it ?