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