protected String updateMergeFactor(String content, String variableName) {
    return content.replaceAll("<mergeFactor>\\{\\{" + variableName + "\\}\\}</mergeFactor>",
            "<mergePolicyFactory class=\"org.apache.solr.index.TieredMergePolicyFactory\">\n" +
                    "      <int name=\"maxMergeAtOnce\">{{" + variableName + "}}</int>\n" +
                    "      <int name=\"segmentsPerTier\">{{" + variableName + "}}</int>\n" +
                    "    </mergePolicyFactory>");
  }
@return a map describing the new LDAP configuration key to the old ambari.properties property name
ambari-server/src/main/java/org/apache/ambari/server/upgrade/UpgradeCatalog270.java