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From Jesse Hallett <halle...@gmail.com>
Subject Re: couchdb Comparison
Date Wed, 07 Oct 2009 16:16:56 GMT
One issue is that Hadoop and CouchDB are very different tools.

Hadoop is great at intensive, high-latency data analysis.  It doesn't matter
how complicated the computation you want is - Hadoop will do it for you
because it is a data processing engine.

CouchDB is a database.  It is designed for low-latency, high-availability
operations.  CouchDB is not a data processing engine, it is a data retrieval
engine.  It should be faster than Hadoop for tasks that both systems can
handle; and CouchDB can perform some powerful analysis via its map-reduce
capability.  But the analysis you can perform with CouchDB will ultimately
be limited by its low-latency design philosophy.

What can be misleading is that while both Hadoop and CouchDB use map-reduce,
they use it for very different things.  It is analogous to saying "these two
programs both use iteration over tree structures."  One detail on choice of
algorithm does not tell you what a program is designed for or what it is
good at.

CouchDB uses map-reduce to build pre-computed views of data.  The map-reduce
pattern enforces data isolation which allows CouchDB to incrementally update
views.  CouchDB does not (yet) take advantage of parallel processing when
generating views.  Though you can get parallelism by distributing data over
a cluster and splitting queries with a proxy.

Hadoop uses map-reduce to run computation in parallel and to distribute
computation across multiple machines.  The same data isolation that CouchDB
relies on allows this.  But Hadoop takes advantage of that feature
differently.

On Oct 7, 2009 7:29 AM, "Göran Krampe" <goran@krampe.se> wrote:

Nicholas Orr wrote: > > On Wed, Oct 7, 2009 at 11:53 PM, Rob Stewart > <
robstewart57@googlemail.com>...
Using an intermediate library in your language of choice you can get queries
etc to look rather similar, take a look at this C# example program for using
Divan:

http://github.com/gokr/Divan/blob/master/samples/Trivial/Program.cs

...funny enough it also uses "Cars" as an example :). Note the LINQ
integration which actually makes it possible to write:

var fastCars = from c in linqCars where c.HorsePowers >= 175 select c;

(given a view for it)

regards, Göran

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