marius adrian popa wrote:

> I will try to see if it can be used with firebird nodes
>
> http://radar.oreilly.com/2009/07/hadoopdb-an-open-source-parallel-database.html
>
>

Before anybody get excited about map/reduce based database systems, it's
important to understand their limitations.

For those unfamiliar with the technology, map/reduce is a technique
pioneered by Google to exploit parallelism across a large number of
potentially unreliable servers. A problem is first broken down in a
finite number of independent tasks (the map phase), which are parceled
out to different servers for execution. The individual results are then
integrated (the reduce phase) and a single answer returned. The reduce
phase also restarts any failed tasks.

Both Google (BigTable) and Amazon (SimpleDB) have built what they call
databases on map/reduce.

The essential limitation of the technology that it is difficult,
probably impossible, to support transactions since, after all, the
various servers are independent. To compensate, both BigTable and
SimpleDB use complex rows that are essentially self defining and support
things like versions and repeating groups. Updates in both systems are
atomic but operate on single rows. This is a data model that works very
well for shopping carts and very poorly for almost everything else.

Map/reduce is very good technology for a large number of computationally
large problems. But I doubt that it has much, if anything, to offer to
database systems.

--
Jim Starkey
Founder, NimbusDB, Inc.
978 526-1376