Method addOldLog

solr/core/src/java/org/apache/solr/update/UpdateLog.java:737–766

(TransactionLog oldLog, boolean removeOld)

    and then decrementing its reference and dropping it.
  */
  @SuppressWarnings(
      "ReferenceEquality") // TransactionLog identity, not equality, is what matters here
  protected synchronized void addOldLog(TransactionLog oldLog, boolean removeOld) {
    if (oldLog == null) return;

    numOldRecords += oldLog.numRecords();

    int currRecords = numOldRecords;

    if (oldLog != tlog && tlog != null) {
      currRecords += tlog.numRecords();
    }

    while (removeOld && logs.size() > 0) {
      TransactionLog log = logs.peekLast();
      int nrec = log.numRecords();
      // remove oldest log if we don't need it to keep at least numRecordsToKeep, or if
      // we already have the limit of 10 log files.
      if (currRecords - nrec >= numRecordsToKeep
          || (maxNumLogsToKeep > 0 && logs.size() >= maxNumLogsToKeep)) {
        currRecords -= nrec;
        numOldRecords -= nrec;
        logs.removeLast().decref(); // dereference so it will be deleted when no longer in use
        continue;
      }

      break;
    }

    // don't incref... we are taking ownership from the caller.
    logs.addFirst(oldLog);
  }