Re: Fetch a SuperColumn based on value of column

[Aaron Morton]

You can use column and super column names with the get_slice() function without 0.7 secondary indexes. I'm assuming that the original query was to test for the existence of a column by name. 

In the case below, to retrieve the full super column would require to request...

First to test the condition. get_slice with a ColumnParent that specifies the CF and the Super Column and a slice predicate with the column_names[] containing the name of the col you want. This query would only return the one column. 

If you then wanted to get all columns in the super column you would make another request. 

If making two requests is a pain or too slow, consider changing the data model to better support the requests you need to make. 

AFAIK a lot of super columns will not impact performance any more than a lot of column. There are however limitations to the number of columns in a super column http://wiki.apache.org/cassandra/CassandraLimitations

 

Hope that helps. 

Aaron

On 03 Dec, 2010,at 01:10 PM, Nick Santini <nick.sant...@kaseya.com> wrote:

actually, the solution would be something like my last mail, but pointing to the name of the super column and the row key

Nicolas Santini

Director of Cloud Computing

Auckland - New Zealand

(64) 09 914 9426 ext 2629

(64) 021 201 3672

On Fri, Dec 3, 2010 at 1:08 PM, Nick Santini <nick.sant...@kaseya.com> wrote:

Hi,

as I got answered on my mail, secondary indexes for super column families is not supported yet, so you have to implement your own

easy way: keep another column family where the row key is the value of your field and the columns are the row keys of your super column family

(inverted index)

Nicolas Santini

Director of Cloud Computing

Auckland - New Zealand

(64) 09 914 9426 ext 2629

(64) 021 201 3672

On Fri, Dec 3, 2010 at 1:00 PM, Narendra Sharma <narendra.sha...@gmail.com> wrote:

Hi,

My schema has a row that has thousands of Super Columns. The size of each super column is around 500B (20 columns). I need to query 1 SuperColumn based on value of one of its column. Something like

SELECT SuperColumn FROM Row WHERE SuperColumn.column="value"

Questions:
1. Is this possible with current Cassandra APIs? If yes, could you please show with a sample.
2. How would such a query perform if the number of SuperColumns is high (> 10K)?

Cassandra version 0.7.

Thanks,
Naren