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https://issues.apache.org/jira/browse/CASSANDRA-3762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13192641#comment-13192641
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Vijay commented on CASSANDRA-3762:
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I dont think it is as bad as it looks.... We aren't doing a lot of random IO
because with this patch Keys are sorted and we will read the same blocks often
and if it is mmapped it will get the most advantage. Also most of the work
load, the keys will not be from the same SST's and 75% of the keys falling into
a SST is not that common IMO (If they do they have a bigger problem because all
their reads are going to be loger and longer) the load time increases if we
have a lot of data in the disk.
I got around 180ms for 3K keys and thats far is the memory in my laptop :)
The other option is to redesign keycache and save the Index location when we
store the keys and then look it up and to fault fill the data which are not in
the cache via (getPosition).... Makes sense?
> 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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