  We study the effect of a single columnar pin on a $(1+1)$ dimensional array
of vortex lines in planar type II superconductors in the presence of point
disorder. In large samples, the pinning is most effective right at the
temperature of the vortex glass transition. In particular, there is a
pronounced maximum in the number of vortices which are prevented from tilting
by the columnar defect in a weak transverse magnetic field. Using
renormalization group techniques we show that the columnar pin is irrelevant at
long length scales both above and below the transition, but due to very
different mechanisms. This behavior differs from the disorder-free case, where
the pin is relevant in the low temperature phase. Solutions of the
renormalization equations in the different regimes allow a discussion of the
crossover between the pure and disordered cases. We also compute density
oscillations around the columnar pin and the response of these oscillations to
a weak transverse magnetic field.
