PlatformLayer adds Solr-as-a-service, 1 day after AWS CloudSearch launch

So; taking stemming as a concrete example:

* With Lucene/Solr, stemming is done with a pluggable class; you can write your rules as a series of exceptions, word by word, but really you'll want to write code for anything non-trivial. Here's an example for Norwegian: http://e-mats.org/2009/05/modifying-a-lucene-snowball-stemme...

AWS only allows word-by-word exceptions, and only allows 500KB. If you need more than 500KB, look like it's more undifferentiated heavy lifting for you...

* With AWS "some basic algorithmic stemming is always performed, such as removing plural suffixes". I think that means you can't turn it off. A lot more documentation is needed there, not least as to what these immutable rules are.

* Solr ships with a bunch of different languages built in; AWS appears only to support English (although I can't believe this is right!)

I'm sure AWS will fix some of these points eventually; but they might not consider it worthwhile to do so, or may not do so on your schedule. With open source, you always have an option.

And this is just stemming! With scoring functions, you're limited to the AWS mini-language, rather than being able to write whatever you want. etc.