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https://issues.apache.org/jira/browse/CASSANDRA-2894?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Byron Clark updated CASSANDRA-2894:
-----------------------------------
Attachment: 2894-with-test.txt
> add paging to get_count
> -----------------------
>
> Key: CASSANDRA-2894
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2894
> Project: Cassandra
> Issue Type: Improvement
> Components: API
> Reporter: Jonathan Ellis
> Priority: Minor
> Labels: lhf
> Fix For: 1.0
>
> Attachments: 2894-formatted.txt, 2894-with-test.txt,
> CASSANDRA-2894.patch
>
>
> It is non-intuitive that get_count materializes the entire slice-to-count on
> the coordinator node (to perform read repair and > CL.ONE consistency). Even
> experienced users have been known to cause memory problems by requesting
> large counts.
> The user cannot page the count himself, because you need a start and stop
> column to do that, and get_count only returns an integer.
> So the best fix is for us to do the paging under the hood, in
> CassandraServer. Add a limit to the slicepredicate they specify, and page
> through it.
> We could add a global setting for count_slice_size, and document that counts
> of more columns than that will have higher latency (because they make
> multiple calls through StorageProxy for the pages).
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