[jira] [Comment Edited] (CASSANDRA-6644) CQL: Select every nth row within the same partition key

["Jorge Bay (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-6644?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13887669#comment-13887669 ] 

Jorge Bay edited comment on CASSANDRA-6644 at 1/31/14 12:32 PM:
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I don't think it matches the requirements of aggregation and filtering of [#CASSANDRA-4914] ...

What I'm proposing is a way to instruct the server how to "move the cursor" when reading a wide row.

When you store data at high rate for measurement / metrics, it is useful to retrieve information at "lower rate" for analysis, but anyway people can vote on it :)



was (Author: jorgebg):
I don't think it matches the requirements of aggregation and filtering of https://issues.apache.org/jira/browse/CASSANDRA-4914 ...

What I'm proposing is a way to instruct the server how to "move the cursor" when reading a wide row.

When you store data at high rate for measurement / metrics, it is useful to retrieve information at "lower rate" for analysis, but anyway people can vote on it :)


> CQL: Select every nth row within the same partition key
> -------------------------------------------------------
>
>                 Key: CASSANDRA-6644
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6644
>             Project: Cassandra
>          Issue Type: Wish
>            Reporter: Jorge Bay
>
> In a time-series schema (like metrics), it is common to create roollups/buckets with datapoints at different rate. 
> It would be nice to have a keyword in CQL to be able to retrieve one every nth row (within a single storage engine wide row).
> For example, in the following schema: 
> CREATE TABLE metrics (
>  ...    metric_id varchar,
>  ...    ts timestamp,
>  ...    value float,
>  ...    PRIMARY KEY (metric_id, ts)
>  ... );
> The following query, will retrieve 1 in every 3 rows:
> (SKIP keyword or something like that, but don't focus on the syntax)
> SELECT ts, value WHERE metric_id = ? SKIP 2;
> This would be very useful for continuous (and somehow linear) metrics.



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