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From Stack <st...@duboce.net>
Subject Re: Beginner question about querying records
Date Sun, 04 Apr 2010 03:56:21 GMT
2010/4/3 Onur AKTAS <onur.aktas@live.com>:
> Hi all,
> I'm thinking of to switch from RDBMS to No-SQL database, but having lots of unanswered
questions in my mind.
> Please correct me if I'm wrong, is Hbase not suitable for small environments? Like if
we have 1 million records with no cluster or maybe 2 machines, is it not required?

It'll work but thats not what its built for.  You'll be better off
sticking with your current RDMBS if your dataset if that size and
going by the rest of your questions below.

> As far as I know, Hbase does not support querying, but having Pig to perform SQL like
queries. It is multi dimensional hashmap distributed across the network to be accessed fast
by key. So if we need to query something then we need to index it by ourselves.


> 1) If we have a user list, and a potential "Give me all people above/beyond age 30" query,
then do we need to create an index from the beginning of the first data as:
> above_30_list : value: [ A, B, C ]beyond_30_list :value: [ X, Y, Z ]   ?

Yes. Or if you can tolerate getting answer offline, run a mapreduce
against the table.

Or, if this is the only query you'll be running , think about how you
could design the primary key so you can answer this question: e.g.

> 2) What if we need just people at age 45. Then do we need to get all above_30 and scan
each of them one by one?
> 3) If we need so many various queries, then should we create such keys as I wrote above
for all potential queries? And entering the data to all that indexes when inserting.

Effectively yes.

> 4) Parallelizing across clusters to share scanning is what HBase or Map Reduce technique
does to solve this issue?
> In short words, I'm willing to switch Hbase for my applications, and wondering how can
I do all these kind of operations in HBase with better performance than I do in RDBMSs.

HBase is about scaling.  To achieve scale, the model is changed.
Moving your RDBMS schema to hbase will take some thought and not all
will make it across.  For a considered thesis on nosql vs rdbms
modeling, see http://j.mp/2PjPB.


> Thanks so much.
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