Custom data-types

Alex De la rosa alex.rosa.box at gmail.com
Fri Aug 29 10:48:34 EDT 2014


Hi Sean,

Seems I was wrong, that makes total sense now that you exposed it, looked a
"too good" feature to me, but seems is not that easy.

By the way, how does "schemas" really work for Riak Search? I went back and
read the documentation but didn't see a real difference from using the
default schema.

Thanks!
Alex


On Fri, Aug 29, 2014 at 3:36 PM, Sean Cribbs <sean at basho.com> wrote:

> Alex,
>
> In short, no, you can't create custom types through schemas. Schemas
> currently only refer to Riak Search 2.
>
> We would love that too, but it hasn't happened yet. The problem is not
> conceiving of a data type but making its behavior both sensible and
> convergent in the face of concurrent activity or network partitions.
> For instance, say that two tweets come in around the same time. Who
> goes first in the "stack" you described? How can multiple independent
> copies reason about which ones to drop from the bottom of the stack to
> keep it bounded to 100? What happens if a replica is separated from
> the others for a while and has really stale entries, is it valid to
> serve those to a user? What happens when one replica pushes an element
> and another one pops it at the same time?
>
> These sound like they might be trivial problems, but they are
> incredibly hard to reason about in the general case. You have to
> reason about the ordering of events, the scope of their effects, and
> decide on a least-surprising behavior to expose to the user. Although
> we have given a pretty familiar/friendly interface to the data types
> shipping in 2.0, their behavior is strictly different from the types
> you would use in a single-threaded program in local memory.
>
> On Thu, Aug 28, 2014 at 4:47 PM, Alex De la rosa
> <alex.rosa.box at gmail.com> wrote:
> > Hi there,
> >
> > Correct me if I'm wrong, but I think I read somewhere that custom
> data-types
> > can be created through schemas or something like that. So, apart from
> > COUNTERS, SETS and MAPS we could have some custom defined ones.
> >
> > I would love to have a STACKS data-type that would work like a FIFO
> stack,
> > so I could save the last 100 objects for some action. Imagine we are
> > building Twitter where millions of tweets are sent all the time, but we
> want
> > to quickly know the last 100 tweets for a user. Imagine something like:
> >
> > obj.stacks['last_tweets'].add(id_of_last_tweet)
> >
> > IN: last_tweet ---> STACK_OF_100_TWEETS ---> OUT: older than the 100th
> goes
> > out
> >
> > Is this possible? If so, how to do it?
> >
> > Thanks and Best Regards,
> > Alex
> >
> > _______________________________________________
> > riak-users mailing list
> > riak-users at lists.basho.com
> > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
> >
>
>
>
> --
> Sean Cribbs <sean at basho.com>
> Software Engineer
> Basho Technologies, Inc.
> http://basho.com/
>
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