  To study environmental effects on the circumgalactic medium (CGM), we use the
samples of redMaPPer galaxy clusters, background quasars and cluster galaxies
from the SDSS. With ~82 000 quasar spectra, we detect 197 MgII absorbers in and
around the clusters. The detection rate per quasar is 2.7$\pm$0.7 times higher
inside the clusters than outside the clusters, indicating that MgII absorbers
are relatively abundant in clusters. However, when considering the galaxy
number density, the absorber-to-galaxy ratio is rather low inside the clusters.
If we assume that MgII absorbers are mainly contributed by the CGM of massive
star-forming galaxies, a typical halo size of cluster galaxies is smaller than
that of field galaxies by 30$\pm$10 per cent. This finding supports that galaxy
haloes can be truncated by interaction with the host cluster.
