It would be queried like any other index as an MR input. I'll create an issue and will try to get this in some time in the next few days - no promises, though.
--- Jeremiah Peschka - Founder, Brent Ozar Unlimited MCITP: SQL Server 2008, MVP Cloudera Certified Developer for Apache Hadoop On Tue, Feb 12, 2013 at 7:09 AM, Kevin Burton <[email protected]>wrote: > I will read the other URLs that you mentioned. Thank you.**** > > ** ** > > Would you mind giving a short example (preferably using CI) of the $keys > index?**** > > ** ** > > *From:* Jeremiah Peschka [mailto:[email protected]] > *Sent:* Tuesday, February 12, 2013 8:52 AM > *To:* Kevin Burton > *Cc:* riak-users > *Subject:* Re: ListKeys or MapReduce**** > > ** ** > > They're both pretty crappy in terms of performance - they read all data > off of disk. If you're using LevelDB you can use the $keys index to pull > back just the keys that in a single bucket.**** > > ** ** > > A better approach is to maintain a separate bucket - e.g. DocumentCount - > that is used for counting documents. Unfortunately, you can't guarantee > transactional consistency around counts in Riak today, so you'll want to > move maintaining the counts out of Riak and into something else. If you > search the list archives [1], you'll find that Redis has been mentioned as > a good way to solve this problem - counters are stored in Redis and flushed > to Riak on a regular schedule. Because of the lack of consistency > (especially around MapReduce operations), Riak isn't the best choice if you > require counters/aggregations to be stored in the database.**** > > ** ** > > Once CRDTs [2] make it into mainstream Riak, you can make use of those > data structures to implement distributed counters in Riak.**** > > ** ** > > [1]: http://riak.markmail.org**** > > [2]: http://vimeo.com/52414903**** > > > **** > > ---**** > > Jeremiah Peschka - Founder, Brent Ozar Unlimited**** > > MCITP: SQL Server 2008, MVP**** > > Cloudera Certified Developer for Apache Hadoop**** > > ** ** > > On Mon, Feb 11, 2013 at 10:30 AM, <[email protected]> wrote:**** > > Say I need to determine how many document there are in my database. For a > CorrugatedIron application I can do ListKeys and get the warning that it is > an expensive operation or I can do a MapReduce query. Which is the the > least expensive? Is there an option that I am missing?**** > > > _______________________________________________ > riak-users mailing list > [email protected] > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com**** > > ** ** >
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