[jira] [Commented] (CASSANDRA-3762) AutoSaving KeyCache and System load time improvements.

["Pavel Yaskevich (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-3762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13192595#comment-13192595 ] 

Pavel Yaskevich commented on CASSANDRA-3762:
--------------------------------------------

With this patch we trade whole sequential primary_index read for random I/O with SSTableReader.getPosition() only for amount saved keys. Can you extend key cache, let's make it 75% of the keys, and run your test again? I think the closer key cache size will get to actual number of keys the worse will performance get...
                
> AutoSaving KeyCache and System load time improvements.
> ------------------------------------------------------
>
>                 Key: CASSANDRA-3762
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3762
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.2
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>             Fix For: 1.2
>
>         Attachments: 0001-SavedKeyCache-load-time-improvements.patch
>
>
> CASSANDRA-2392 saves the index summary to the disk... but when we have saved cache we will still scan through the index to get the data out.
> We might be able to separate this from SSTR.load and let it load the index summary, once all the SST's are loaded we might be able to check the bloomfilter and do a random IO on fewer Index's to populate the KeyCache.

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