The present invention relates to a downhole hydraulic pump for providing fluid pressure during downhole operations, comprising a pump housing, a cam shaft rotatably arranged in the pump housing and having a longitudinal spin axis, the cam shaft comprising a shaft and a cam lobe arranged on the shaft, a radially arranged piston having a housing end and a cam end, a piston housing arranged in the pump housing, an inlet valve arranged in an inlet in the piston housing, an outlet valve arranged in an outlet in the piston housing, and a piston spring arranged in the pump housing for moving the piston away from the piston housing, wherein the piston housing is rotatably connected to the pump housing enabling rotation of the piston housing around a piston housing rotation axis parallel to the longitudinal spin axis of the cam shaft.