[jira] [Updated] (CASSANDRA-4304) Add bytes-limit clause to queries

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-4304?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jonathan Ellis updated CASSANDRA-4304:
--------------------------------------

    Fix Version/s:     (was: 1.2.0)
    
> Add bytes-limit clause to queries
> ---------------------------------
>
>                 Key: CASSANDRA-4304
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4304
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: API, Core
>            Reporter: Christian Spriegel
>         Attachments: TestImplForSlices.patch
>
>
> Idea is to add a second limit clause to (slice)queries. This would allow easy loading of batches, even if content is variable sized.
> Imagine the following use case:
> You want to load a batch of XMLs, where each is between 100bytes and 5MB large.
> Currently you can load either
> - a large number of XMLs, but risk OOMs or timeouts
> or
> - a small number of XMLs, and do too many queries where each query usually retrieves very little data.
> With cassandra being able to limit by size and not just count, we could do a single query which would never OOM but always return a decent amount of data -- with no extra overhead for multiple queries.
> Few thoughts from my side:
> - The limit should be a soft limit, not a hard limit. Therefore it will always return at least one row/column, even if that one large than the limit specifies.
> - HintedHandoffManager:303 is already doing a InMemoryCompactionLimit/averageColumnSize to avoid OOM. It could then simply use the new limit clause :-)
> - A bytes-limit on a range- or indexed-query should always return a complete row

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