Greater than equals query and LIMIT with Pycassa

[Dan Theirl]

Hello,

I am having a really hard time finding out the best way to do this CQL query with Pycassa.  I have found a nasty work around with thrift and execute_cql3_query but that's not fun to parse and creates a mess in my code.  Is there a easier pycassa way to do this:

"SELECT * FROM geoIPblock WHERE startIpNum >= 839593873 LIMIT 1"

I am wondering if I should just use python-cql and drop pycassa all together.

Thank you so much in advance!

Dan

[Tyler Hobbs]

It's generally not a good idea to mix cql3 and pycassa.  The only tables that pycassa can interact with through its normal API are cql3 tables that are created WITH COMPACT STORAGE.  (See http://www.datastax.com/dev/blog/cql3-for-cassandra-experts for more details.)

I don't know what your schema is, so I can't suggest how to do something equivalent in pycassa.

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Tyler Hobbs
DataStax

[Dan Theirl]

Okay thanks Tyler,

Here is my schema:

startIpNum is Primary Key LongType

endIpNum is Secondary Index LongType

locId is IntegerType

column_type Standard

comparator_type UTF8Type

subcomparator_type None

key_validation_class LongType

default_validation_class LongType

gc_grace_seconds 864000

There's a 4-5 million rows, let me know if there is any other information you need.

Thanks,

Dan

[Kumar Ranjan]

Dan,

There is no such thing in Pycassa (MongoDB has something called Criteria where you can specify conditions, based on which results are returned, more like WHERE clause in RDBMS). Its very important piece missing in Pycassa. You would have to do this in your code like I do but then it makes code do tremendous amount of extra work or parsing and throwing unnecessary data and keep what you need. No fun. This has annoyed our team so much so that a decision was made to move to MongoDB.

Hope it helps.

-- K

[Tyler Hobbs]

On Fri, Mar 7, 2014 at 10:08 AM, Kumar Ranjan <winne...@gmail.com> wrote:

There is no such thing in Pycassa (MongoDB has something called Criteria where you can specify conditions, based on which results are returned, more like WHERE clause in RDBMS). Its very important piece missing in Pycassa. You would have to do this in your code like I do but then it makes code do tremendous amount of extra work or parsing and throwing unnecessary data and keep what you need.

For what it's worth, you certainly can do operations like this, although they tend to be clearer in CQL than through the pycassa API (for most users and use cases).  Additionally, data modeling in Cassandra is much different from how you would model your data in a relational database or a document database.  If you try to treat Cassandra like an RDBMS, you're not going to have a fun time.


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Tyler Hobbs
DataStax

[Kumar Ranjan]

Tyler,

Can you please elaborate on this, 'For what it's worth, you certainly can do operations like this' ? How would you specify criteria (aka where clause) in get, xget or get_range() in pycassa? I understand CQL is the way going forward but dealing with tons of legacy stuff here which uses Pycassa.

Regards,

-- Kumar

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[Tyler Hobbs]

Your "where clause" tools are effectively specifying the row key(s) and a column slice (or set of column names).  As I said, data modelling is not the same in Cassandra as in an RDBMS or a document store.  You have to model your queries, not your objects and their relationships.  Effectively, you are pre-building support for the "where clauses" you want to support.

I suggest watching some of Patrick's videos here: http://wiki.apache.org/cassandra/DataModel

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Tyler Hobbs
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[Kumar Ranjan]

I agree and thanks. Will checkout the video.

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