private void applyToMemStore(HStore store, List<ExtendedCell> cells, boolean delta,
    MemStoreSizing memstoreAccounting) {
    // Any change in how we update Store/MemStore needs to also be done in other applyToMemStore!!!!
    boolean upsert = delta && store.getColumnFamilyDescriptor().getMaxVersions() == 1;
    if (upsert) {
      store.upsert(cells, getSmallestReadPoint(), memstoreAccounting);
    } else {
      store.add(cells, memstoreAccounting);
    }
  }
@param delta If we are doing delta changes -- e.g. increment/append -- then this flag will be
             set; when set we will run operations that make sense in the increment/append
             scenario but that do not make sense otherwise.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java