| Package | Description | 
|---|---|
| io.druid.query.aggregation.cardinality | |
| io.druid.query.aggregation.hyperloglog | 
| Class and Description | 
|---|
| HyperLogLogCollector
 Implements the HyperLogLog cardinality estimator described in:
 http://algo.inria.fr/flajolet/Publications/FlFuGaMe07.pdf
 Run this code to see a simple indication of expected errors based on different m values:
  
 for (int i = 1; i < 20; ++i) {
   System.out.printf("i[%,d], val[%,d] => error[%f%%]%n", i, 2 << i, 104 / Math.sqrt(2 << i));
 }
 
 This class is *not* multi-threaded. | 
| Class and Description | 
|---|
| HyperLogLogCollector
 Implements the HyperLogLog cardinality estimator described in:
 http://algo.inria.fr/flajolet/Publications/FlFuGaMe07.pdf
 Run this code to see a simple indication of expected errors based on different m values:
  
 for (int i = 1; i < 20; ++i) {
   System.out.printf("i[%,d], val[%,d] => error[%f%%]%n", i, 2 << i, 104 / Math.sqrt(2 << i));
 }
 
 This class is *not* multi-threaded. | 
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