A function as an input for map/reduce

Mikhail Sobolev mss at mawhrin.net
Tue May 3 17:55:37 EDT 2011


I watched "MapReducing Big Data With Riak and Luwak"[1] recorded
webinar.  And it is based on a possibility to use a function ("dynamic
inputs" @ ~8:04 in the video) to actually generate inputs for the query.

It raised two questions:

1. Is there a documentation about this kind of function?  (parameters,
   requirements, limitations, general comments)

2. Is there more information about "it can through a few keys at a time,
   and the map/reduce chain would go ahead and start doing the
   processing on whatever keys it gets as soon as it gets them, it does
   not have to wait for the whole list of that function" (@ ~9:54 in the
   video)?  What I'm concerned here is about a chain of
   map/map/map/reduce/reduce phases.   How the processing is actually
   performed?  What are the synchronization points?


[1] http://vimeo.com/20074937
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