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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: Using CQL to insert a column to a row dynamically
Date Mon, 27 May 2013 17:10:23 GMT
You can add wide rows to CQL3 tables but you can not add wide rows in the
same way you can for non-cql-3 compact storage tables.

"What I'm not understanding is why there is so much emphasis to predefined
columns in CQL examples, particularly in the CREATE TABLE/COLUMNFAMILY
examples:"

^ I ask myself this all the time. I wrote a piece on it a while back.
http://www.edwardcapriolo.com/roller/edwardcapriolo/entry/schema_vs_schema_less

IMHO there seems to be a huge over-emphasis in pushing the new X, the new
Y, or the new way of doing things. There are several very nice things in
CQL, especially when it comes to packing up complex composite types, but
there are several things it can't do well.

One thing that greatly erks me, if you followed the older advice on how to
do something with cassandra 1.0.7, there is sometimes new advice on how to
do the same thing in 1.2.5.  From reading the new documentation you might
come to the conclusion that the old way or old tools are wrong or bad, but
there are a large group of people that actually like the old ways better!
Your example is the most simple case "should I be able to add columns?"
Yes! Can you? Yes! but not using the new stuff. (well it can be done but no
exactly the same way).

My best advice is just one of those things where you read all available
material and make a decision on what is best for your case. Use the system
that works best with the least hoop jumping.

In a nutshell its very easy to had true schema-less wide rows without the *
and the 'read the blog' use compact storage :)




On Mon, May 27, 2013 at 10:42 AM, Hiller, Dean <Dean.Hiller@nrel.gov> wrote:

> Wide rows, dynamic columns are still possible in CQL3.  There are some
> links here http://comments.gmane.org/gmane.comp.db.cassandra.user/30321
>
> Also, there are other advantages to noSQL, not just schemaless aspect such
> as that it can accept tons of writes and you can scale the writes(you can't
> do that with an RDBMS).  With an RDBMS you can typically scale the reads
> with backups and stuff but there is limits here too.  There are not limits
> with noSQL…just double your nodes and get double the read throughput. This
> has nothing to do with how much you can store at all.  You maybe are only
> storing 200G with an amazing write/read throughput including TONS of
> deletes to keep it under 200G.
>
> That comes to the next advantage….store huge amounts of data.  If you have
> 1000 machines and 300G on each machine, you are storing 300T or 1/3
> Petabytes.  Have fun with an RDBMS.
>
> So yes, schemaless is one advantage, throughput is another, total storage
> room is yet another.  HA is probably debatable, but in my opinion HA has
> been another advantage we have seen.  We have had a hardware outage and no
> downtime already with cassandra whereas on a previous project oracle RAC
> did not really hold up to it's promises.  There may be another advantage I
> may be missing as well.
>
> Also, PlayOrm for java client currently uses thrift(astyanax specifically)
> and so do a ton of projects right now.  I know PlayOrm is about to upgrade
> to CQL3 as well so it can do thrift or CQL3 in the future.
>
> Later,
> Dean
>
> From: Matthew Hillsborough <matthew.hillsborough@gmail.com<mailto:
> matthew.hillsborough@gmail.com>>
> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <
> user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
> Date: Monday, May 27, 2013 8:28 AM
> To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <
> user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
> Subject: Using CQL to insert a column to a row dynamically
>
> Hi all,
>
> I posted a similar thread on stackoverflow - hope it's not repetitive for
> anyone here. Looking for better insight from the community on whether
> Cassandra is the right tool for me or not.
>
> I am trying to understand some fundamentals in Cassandra, I was under the
> impression that one of the advantages a developer can take in designing a
> data model is by dynamically adding columns to a row identified by a key.
> That means I can model my data so that if it makes sense, a key can be
> something such as a user_id from a relational database, and I can for
> example, create arbitrary amounts of columns that relate to that user.
>
> What I'm not understanding is why there is so much emphasis to predefined
> columns in CQL examples, particularly in the CREATE TABLE/COLUMNFAMILY
> examples:
>
> CREATE TABLE emp (
>
>   empID int,
>
>   deptID int,
>
>   first_name varchar,
>
>   last_name varchar,
>
>   PRIMARY KEY (empID, deptID)
>
> );
>
> Wouldn't this type of model make more sense to just stuff into a
> relational database? What if I don't know my column name until runtime and
> need to dynamically create it? Do I have to use ALTER TABLE to add a new
> column to the row using CQL? The particular app use-case I have in mind I
> would just need a key identifier and arbitrary column names where the
> column name might include a timestamp+variable_identifier. The whole point
> is that so I can see have extremely wide rows at the wonderful performance
> that Cassandra has to offer. As of right now, from everything I'm reading
> in regards to DataStax recommending CQL over Thrift (I think what I'm
> describing is possible with Thrift, but correct me if I'm wrong). That
> means I'd have to go AGAINST the recommendation to a protocol that's pretty
> much going to eventually not be supported.
>
> Is Cassandra the right tool for that? Are the predefined columns in
> documentation nothing more than an example? How does one add a dynamic
> column name with an existing column family/table? If I'm stuck with static
> columns, how is this any different than using a relational database such as
> postgres or mysql? What I found really powerful about Cassandra is being
> able to do something like the following in cassandra-cli which uses Thrift:
>
>
> SET mycf[id]['arbitrary_column'] = 'foo';
>
> However, doing that in CQL isn't possible. Completely limits the way I was
> going to model my data for an application and would have no distinct
> advantage over a relational database.
>
>
> Please tell me I'm an idiot and/or am wrong and how I can make this work.
> It seems Thrift is the only solution, but I hate going against the
> recommended protocol.
>
>
> Thanks.
>

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