Redis

ZUNIONSTORE destination numkeys key [key ...] [WEIGHTS weight [weight ...]] [AGGREGATE SUM|MIN|MAX]

Computes the union of numkeys sorted sets given by the specified keys, and stores the result in destination. It is mandatory to provide the number of input keys (numkeys) before passing the input keys and the other (optional) arguments.

By default, the resulting score of an element is the sum of its scores in the sorted sets where it exists.

Using the WEIGHTS option, it is possible to specify a multiplication factor for each input sorted set. This means that the score of every element in every input sorted set is multiplied by this factor before being passed to the aggregation function. When WEIGHTS is not given, the multiplication factors default to 1.

With the AGGREGATE option, it is possible to specify how the results of the union are aggregated. This option defaults to SUM, where the score of an element is summed across the inputs where it exists. When this option is set to either MIN or MAX, the resulting set will contain the minimum or maximum score of an element across the inputs where it exists.

If destination already exists, it is overwritten.

Return value

Integer reply: the number of elements in the resulting sorted set at destination.

Examples

redis>  ZADD zset1 1 "one"
(integer) 1
redis>  ZADD zset1 2 "two"
(integer) 1
redis>  ZADD zset2 1 "one"
(integer) 1
redis>  ZADD zset2 2 "two"
(integer) 1
redis>  ZADD zset2 3 "three"
(integer) 1
redis>  ZUNIONSTORE out 2 zset1 zset2 WEIGHTS 2 3
(integer) 3
redis>  ZRANGE out 0 -1 WITHSCORES
1) "one"
2) "5"
3) "three"
4) "9"
5) "two"
6) "10"
redis> 
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