Package com.blackrook.redis.commands

Interface RedisHyperlogCommands

All Known Implementing Classes:

RedisConnection

public interface RedisHyperlogCommands

Interface for Redis HyperlogLog management.

Author:

Matthew Tropiano

Method Summary

Modifier and Type	Method	Description
boolean	pfadd(String key, String element, String... elements)	From http://redis.io/commands/pfadd:
long	pfcount(String key, String... keys)	From http://redis.io/commands/pfcount:
boolean	pfmerge(String destkey, String sourcekey, String... sourcekeys)	From http://redis.io/commands/pfmerge:

Method Detail

pfadd

boolean pfadd(String key,
              String element,
              String... elements)

From http://redis.io/commands/pfadd:

Available since 2.8.9.

Time complexity: O(1) to add every element.

Adds all the element arguments to the HyperLogLog data structure stored at the variable name specified as first argument.

Parameters:

key - the hyperlog key.

element - the first element.

elements - the rest of the elements.

Returns:

true if at least one internal register was altered, false otherwise.

pfcount

long pfcount(String key,
             String... keys)

From http://redis.io/commands/pfcount:

Available since 2.8.9.

Time complexity: O(1).

Returns the approximated cardinality computed by the HyperLogLog data structure stored at the specified variable, which is 0 if the variable does not exist.

Parameters:

key - the first key.

keys - the rest of the keys.

Returns:

the number of unique elements observed via pfadd(String, String, String...).

pfmerge

boolean pfmerge(String destkey,
                String sourcekey,
                String... sourcekeys)

From http://redis.io/commands/pfmerge:

Available since 2.8.9.

Time complexity: O(N) to merge N HyperLogLogs, but with high constant times.

Merge multiple HyperLogLog values into an unique value that will approximate the cardinality of the union of the observed Sets of the source HyperLogLog structures.

Parameters:

destkey - the destination key.

sourcekey - the first key.

sourcekeys - the rest of the keys.

Returns:

always true.