code: public long getColumnCardinality(String schema, String table, Authorizations auths, String family, String qualifier, Collection<Range> colValues)
              throws ExecutionException
      {
          LOG.debug("Getting cardinality for %s:%s", family, qualifier);
  
          // Collect all exact Accumulo Ranges, i.e. single value entries vs. a full scan
          Collection<CacheKey> exactRanges = colValues.stream()
                  .filter(ColumnCardinalityCache::isExact)
                  .map(range -> new CacheKey(schema, table, family, qualifier, range, auths))
                  .collect(Collectors.toList());
  
          LOG.debug("Column values contain %s exact ranges of %s", exactRanges.size(), colValues.size());
  
          // Sum the cardinalities for the exact-value Ranges
          // This is where the reach-out to Accumulo occurs for all Ranges that have not
          // previously been fetched
          long sum = cache.getAll(exactRanges).values().stream().mapToLong(Long::longValue).sum();
  
          // If these collection sizes are not equal,
          // then there is at least one non-exact range
          if (exactRanges.size() != colValues.size()) {
              // for each range in the column value
              for (Range range : colValues) {
                  // if this range is not exact
                  if (!isExact(range)) {
                      // Then get the value for this range using the single-value cache lookup
                      sum += cache.get(new CacheKey(schema, table, family, qualifier, range, auths));
                  }
              }
          }
  
          return sum;
      }
docs: Gets the column cardinality for all of the given range values. May reach out to the
  metrics table in Accumulo to retrieve new cache elements.
  
  @param schema Table schema
  @param table Table name
  @param auths Scan authorizations
  @param family Accumulo column family
  @param qualifier Accumulo column qualifier
  @param colValues All range values to summarize for the cardinality
  @return The cardinality of the column