I am only speaking to your second question.

It may be helpful to think of modeling your storage layout in terms of
* lists
* sets
* hash maps
... and certain combinations of these.

Since there are no schema-defined relations, your relations may appear implicit between different views or "copies" of your data. The relationship can be assumed to be explicit to the extent that it is used in that way or even (in some cases) enforced by a boundary layer in your software.

For accessing data by value, you can try to do your bookkeeping (indexing) as you go, by maintaining auxiliary maps directly via your application. Scanning by value is really not a strong point for Cassandra, and in fact is one of the trade-offs made when moving to a DHT (http://en.wikipedia.org/wiki/Distributed_hash_table) data store.

There has been discussion around putting some form of value indexing in at some point in the future, but the plans appear indefinite. Even with this, it would move workload into the hub which may otherwise be better handled in a client node.


On Sun, May 2, 2010 at 4:33 PM, CleverCross | Falk Wolsky <falk.wolsky@clevercross.eu> wrote:
Hello,

1) Can you provide a solution or a sample for searching (Column and SuperColumn) (Fulltext).
What is the Way to realize this? Hadoop/MapReduce? See you a posibility to build/use a index for columns?

Why this: In a given Data-Model we "must" use UUIDs as Key and have actually no chance to seach values from "Columns"? (or not?)

2) How can we realize a "relation"

For Sample: (http://arin.me/blog/wtf-is-a-supercolumn-cassandra-data-model)
Arin describes good a simple Data-Model to build a Blog. But how can we read (filter) all Posts from "BlogEntries" from a single Autor?
(filter the Supercolumns by a culum inside of a SuperColumn)

The "relation" for Sample is Autor -> BlogEntries...
To filter the Datas there is a needing to specify in a "get(...)"-Function a Column/Value combination...

I know well that cassandra is not a "relational Database"! But without these releations the usage is very "limited" (specialized)

Thanks in Advance! - and thx for Cassandra!
With Hector i build a (Apache)Cocoon-Transformer...

With Kind Regards,
Falk Wolsky