Erlang Client Example for using links in map/reduce

Paul Jones pauljones23 at
Sat Oct 10 11:12:35 EDT 2009

Hi Bryan,

On Sat, Oct 10, 2009 at 2:41 PM, Bryan Fink <bryan at> wrote:

> I'll describe how to manage objects you have requested over the HTTP
> interface, since I expect that's what most people are dealing with.

I'm actually using the Erlang interface, so I poked into the Erlang code a

For now, I'll just give a clue about how you could support links in an
> entirely different format of data inside Riak (using the raw-Erlang
> interface instead of the HTTP interface): grep linkfun src/*.erl.  If
> someone is really interested in such things, and needs a few more
> pointers, I'll write a second how-to.
So my understanding of this, after looking through the code is that a {link,
_, _, _} tag simply transforms into a map phase, using whatever link
function is associated with the bucket.  So if I wanted to the same thing in
the native Erlang, I take it that I have two options: associate a linkfun
with the bucket, and use {link,_,_,_}; or simply specify two map phases -
the first to extract a set of {bucket, key} or {{bucket, key}, data} tuples;
the second phase then processing the values loaded as a result of these
phases, returning values ready for a reduce function.

Am I right in this understanding?

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