Looking for good tutorial on writing Erlang Map/Reduce queries?

Derek Sanderson zapphutz at gmail.com
Wed Jan 16 16:58:35 EST 2013


Thanks so much for pointing me to your examples. I'll definitely be looking
them over.

As for the "official" map/reduce stuff that comes with Riak, all I can say
is "why didn't I think of that?".

Thanks again

On Wed, Jan 16, 2013 at 4:18 PM, Christian Dahlqvist <christian at basho.com>wrote:

> Hi Derek,
> The best place to start is probably the mapreduce functions officially
> included in Riak (
> https://github.com/basho/riak_kv/blob/master/src/riak_kv_mapreduce.erl)
> if you have not already found these. These do however not make use of
> arguments. If you are looking for an example of how arguments can be used,
> you could look at a little library containing map phase functions that I
> wrote some time back. In these I accept JSON documents as arguments and use
> this to control processing. The library is available here:
> https://github.com/whitenode/riak_mapreduce_utils
> Best regards,
> Christian
> On 16 Jan 2013, at 13:34, Derek Sanderson <zapphutz at gmail.com> wrote:
> Hello all,
> Been googling around, but failing to find anything that really helps walk
> a newcomer through writing M/R queries in Erlang for Riak.
> I'm going through some general Erlang tutorials, but it would also be good
> to just see some solid examples of basic (and not so basic) Map and Reduce
> operations, to get a feel for how to actually write them. The Riak Handbook
> has one example that I've been going with, which is good for a bare-minimum
> set of requirements for how to write these, but doesn't really provide
> enough info to know what kinds of things are available to me, and some
> common patterns to apply in writing my own Maps, how to pass in parameters,
> etc etc.
> Thanks in advance
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