@Override
    public Path call() throws Exception {
      return processPathDepthInfo(pd);
    }
Assume that depth is 2, i.e., partition columns are a and b
tblPath/a=1  => throw exception
tblPath/a=1/file => throw exception
tblPath/a=1/b=2/file => return a=1/b=2
tblPath/a=1/b=2/c=3 => return a=1/b=2
tblPath/a=1/b=2/c=3/file => return a=1/b=2

@param basePath
         Start directory
@param allDirs
         This set will contain the leaf paths at the end.
@param partColNames
         Partition column names
@throws IOException
          Thrown if we can't get lists from the fs.
@throws MetastoreException ex
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/HiveMetaStoreChecker.java