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Re: NoSQL -vs- SQL

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>>>>> "Carlos" == Carlos Mennens <carlos.mennens@xxxxxxxxx> writes:

Carlos> Looking to read your feedback and / or opinions.

Here's what I wrote on the Smalltalk Seaside mailing list a few weeks
back:


I've given a talk a few times about "forget the ORM".  The slides are up 
on http://www.slideshare.net/RandalSchwartz/forget-the-orm

The key thing that separates a lot of these newer databases is that you 
can't have all three of consistency, availability, and performance at 
once... you have to sacrifice something.  Traditional SQL databases 
favored consistency over everything, but who cares if your blog page 
says "read the 6 comments on this item" for a couple of seconds when 
there are really 7 because one just got added. 

The new databases give options for higher availability or performance at 
the cost of consistency.  Some, like Riak (interviewed at 
http://twit.tv/floss129), actually let you select on each request how 
consistent you want the results, thus controlling how fast you get the 
response.  Thus, for the front page of a blog, you can say "give me a 
result that any 1 of the 3 replicas has", but when you finally drill 
into the comments, you say "give me a result that all 3 replicas agree 
on".  Of course, these are all *eventually* consistent on the order of 
tens or hundreds of milliseconds, but by allowing "almost correct" 
results, things are a lot zippier.  (It also works that way on 
write... you can say "come back when any 1 replica says it has it" or 
"come back only when all 3 replicas confirm write".) 

So, it's not so much that you get schemaless key/value store (although 
that's a frequent feature)... it's that these aren't traditional 
databases in a lot of ways. 


-- 
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<merlyn@xxxxxxxxxxxxxx> <URL:http://www.stonehenge.com/merlyn/>
Smalltalk/Perl/Unix consulting, Technical writing, Comedy, etc. etc.
See http://methodsandmessages.posterous.com/ for Smalltalk discussion

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