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https://issues.apache.org/jira/browse/CASSANDRA-8861?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14995175#comment-14995175
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Martin Herren commented on CASSANDRA-8861:
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You got one more fanboy for this. Love the fact that Redis has a builtin HLL
type.
Either as a data type, or as a table type as for counter tables. It could also
be an enhancement of counter tables so they could have counters and hlls
columns.
Either way i'd like to see this feature !
> HyperLogLog Collection Type
> ---------------------------
>
> Key: CASSANDRA-8861
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8861
> Project: Cassandra
> Issue Type: Wish
> Reporter: Drew Kutcharian
> Fix For: 3.x
>
>
> Considering that HyperLogLog and its variants have become pretty popular in
> analytics space and Cassandra has "read-before-write" collections (Lists), I
> think it would not be too painful to add support for HyperLogLog "collection"
> type. They would act similar to CQL 3 Sets, meaning you would be able to
> "set" the value and "add" an element, but you won't be able to remove an
> element. Also, when getting the value of a HyperLogLog collection column,
> you'd get the cardinality.
> There are a couple of good attributes with HyperLogLog which fit Cassandra
> pretty well.
> - Adding an element is idempotent (adding an existing element doesn't change
> the HLL)
> - HLL can be thought of as a CRDT, since we can safely merge them. Which
> means we can merge two HLLs during read-repair. But if that's too much work,
> I guess we can even live with LWW since these counts are "estimates" after
> all.
> There is already a proof of concept at:
> http://vilkeliskis.com/blog/2013/12/28/hacking_cassandra.html
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