private void overrideMRProps(JobConf job, Map<String, String> properties) {
    for (String key : properties.keySet()) {
      if (key.startsWith(COMPACTOR_PREFIX)) {
        String mrKey = key.substring(10); // 10 is the length of "compactor." We only keep the rest.
        job.set(mrKey, properties.get(key));
      }
    }
  }
Parse tblproperties to override relevant properties of compactor MR job with specified values.
For example, compactor.mapreuce.map.memory.mb=1024
@param job the compactor MR job
@param properties table properties
ql/src/java/org/apache/hadoop/hive/ql/txn/compactor/MRCompactor.java