On 16/10/2013 11:51 AM, Ze'ev Atlas wrote:
Since NoSQL seems to be reigning supreme, I decided to study MongoDB which was
both recommended by a friend (a PM who is managing an actual project with that
stuff) and is the most popular NoSQL engine out there according to
http://db-engines.com/en/ranking (they don't count Hadoop since they considered
it to be a file system.)
As usual, I acquired the book (O'Reilly - mongodb the definitive guide) and
began to read...
And here is why I post it here, I have the sense of deja vu all over again!
Forget about the fancy terminology of storing "Documents" rather then rows or
records. In the end it is the same. They have all the CRUD actions (i.e. Create,
Remove, Update and Delete) which are done via some API functions rather then SQL
statements. They can index and access stuff fast. They can partition the database over
many servers and thus scale out... all is good.
But here is the real scoop! No Joins and if you want to store some row...
er... document of different structure that relate to the current one, you'd
rather store it as a sub document (i.e. a different structure that is part of
your current row (i.e. hierarchical) or in a different collection that you
should navigate into in the application side.
Mmm, have I just used the words navigate, hierarchical, etc. No wonder that
all those younger people are so excited about NoSQL, they have never seen it
before. But we, veterans of IMS, IDMS, ADABAS and the like, our old skills are
new again!
We had a conversation on linkedin wrt comparing IMS to MongoDB
http://tinyurl.com/mk95nrq. I fail to see any similarity between the two
other than they are both data bases, have keys and values.
MongoDB stores it data in BSON or binary JSON and is schema-less. That's
a good thing for some applications, think CMS, and companies that
release software continuously. The guardian replaced Oracle
with MongoDB and it was the right tool for the job
http://www.slideshare.net/tackers/why-we-chose-mongodb-for-guardiancouk#!.
It is not, however, a drop in replacement for traditional transactional
data bases.
Welcome back to the future.
----------------
BTW, I do not bad mouth the technology, it is very useful (as were IMS and
IDMS) and I can see replacing all warehouses and Star Schemas with that stuff,
it is more natural, faster and more scalable then the current SQL based
warehouse technologies.
ZA
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