@Override
                public Long call() throws Exception {
                  long len = getPathLength(jobConf, path, partition.getInputFormatClass(), threshold);
                  LOG.trace(path + ", length=" + len);
                  return total.addAndGet(len);
                }
Tries to convert simple fetch query to single fetch task, which fetches rows directly
from location of table/partition.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/SimpleFetchOptimizer.java