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On May 3, 2016, at 6:45 AM, Miles Gould <mgould at redhat.com> wrote:

>> This DB could be an RDBMS or Cassandra, depending on the deployer's preferences
> AFAICT this would mean introducing and maintaining a layer that abstracts over RDBMSes and Cassandra. That's a big abstraction, over two quite different systems, and it would be hard to write code that performs well in both cases. If performance in this layer is critical, then pick whichever DB architecture handles the expected query load better and use that.

Agreed - you simply can’t structure the data the same way. When I read criticisms of Cassandra that include “you can’t do joins” or “you can’t aggregate”, it highlights this fact: you have to think about (and store) your data completely differently than you would in an RDBMS. You cannot simply abstract out the differences.

-- Ed Leafe