@Override
    public void close() throws IOException {
      if (this.deleteRecords != null) {
        this.deleteRecords.close();
      }
    }
An implementation for DeleteEventRegistry that opens the delete delta files all
at once, and then uses the sort-merge algorithm to maintain a sorted list of
delete events. This internally uses the OrcRawRecordMerger and maintains a constant
amount of memory usage, given the number of delete delta files. Therefore, this
implementation will be picked up when the memory pressure is high.

Don't bother to use KeyInterval from split here because since this doesn't
buffer delete events in memory.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/VectorizedOrcAcidRowBatchReader.java