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From Christian van der Leeden <christian.vanderlee...@googlemail.com>
Subject Re: Learning-by-doing (also announcing a new Ruby Client Codename: "Greek Architect")
Date Sat, 19 Jun 2010 16:30:28 GMT
Hi Thomas,

	did you look at cassandra gem from twitter (fauna/cassandra) on github?
They also use the thrift_client and already have the basic cassandra API accessible.

I'm also using ruby with cassandra and still need to find a slick way to do the inserts
and when to update the indexes. 

If I understood correctly you want to look up a user by name. And you want to have
the name as row keys where you would find the UID with which you could look up your user?

From my understanding I would put the index into one row, name it e.g. "user_by_name",
and insert columns where the column name is the user name and the value of the column
would be the UUID of the user. Cassandra creates the index on the column names. You can
efficiently insert new values into this row.

What do you want to do with the users partitioned by date? Sorted by creation date? Login
date?

For the cascading deletes: a database would have to remove a record from its index, too.
In Cassandra you would have to do it yourself..

Christian

On Jun 19, 2010, at 3:27 AM, Thomas Heller wrote:

> Howdy!
> 
> So, last week I finally got around to playing with Cassandra. After a
> while I understood the basics. To test this assumption I started
> working on my own Client implementation since "Learning-by-doing" is
> what I do and existing Ruby Clients (which are awesome) already
> abstracted too much for me to really grasp what was going on. Java is
> not really my thing (anymore) so I began with the Thrift API and Ruby.
> 
> Anyways back to Topic.
> 
> This library is now is available at:
> http://github.com/thheller/greek_architect
> 
> Since I have virtually no experience with Cassandra (but plenty with
> SQL) I started with the first use-case which I have programmed a bunch
> of times before. User Management. I build websites which are used by
> other people, so I need to store them somewhere.
> 
> Step #1: Creating Users and persisting them in Cassandra
> 
> Example here:
> http://github.com/thheller/greek_architect/blob/master/spec/examples/user_create_spec.rb
> 
> I hope my rspec-style documentation doesnt confuse too many people
> since I already have a gazillion questions for this simple, but also
> VERY common use-case. Since a question is best asked with a concrete
> example to refer to, here goes my first one:
> 
> Would any of you veterans build what I built the way I did? (refering
> to the cassandra design, not the ruby client)
> 
> I insert Users with UUID keys into one ColumnFamily. I then index them
> by creating a row in another ColumnFamily using the Name as Key and
> then adding one column holding a reference to the User UUID. I also
> insert a reference into another ColumnFamily holding a List of Users
> partitioned by Date.
> 
> I'm really unsure about the index design, since they dont get updated
> when a User row is removed. I could hook into the remove call (like I
> did into mutations) and cascade the deletes where needed, but 10+
> years of SQL always want to tell me I'm crazy for doing this stuff!
> 
> I'd really appreciate some feedback.
> 
> Cheers,
> Thomas


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