@Override
  public void preFlushScannerOpen(ObserverContext<? extends RegionCoprocessorEnvironment> c,
    Store store, ScanOptions options, FlushLifeCycleTracker tracker) throws IOException {
    options.readAllVersions();
  }
An example for implementing a counter that reads is much less than writes, i.e, write heavy.
<p>
We will convert increment to put, and do aggregating when get. And of course the return value of
increment is useless then.
<p>
Notice that this is only an example so we do not handle most corner cases, for example, you must
provide a qualifier when doing a get.
hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/WriteHeavyIncrementObserver.java