@Override
  public void onRegionMerged(RegionInfo mergedRegion) throws IOException {
    if (initialized) {
      namespaceQuotaManager.updateQuotaForRegionMerge(mergedRegion);
    }
  }
Returns cached region count, or -1 if quota manager is disabled or table status not found
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/MasterQuotaManager.java