public  int calculateListBucketingLevel() {
    int lbLevel = isSkewedStoredAsDir() ? this.getSkewedColNames().size() : 0;
    return lbLevel;
  }
Calculate list bucketing level.

0: not list bucketing
int: no. of skewed columns

@return
ql/src/java/org/apache/hadoop/hive/ql/plan/ListBucketingCtx.java