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https://issues.apache.org/jira/browse/CASSANDRA-2392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13189802#comment-13189802
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Pavel Yaskevich commented on CASSANDRA-2392:
--------------------------------------------

bq. Renamed and done recommended changes. Exempt we have all the in-memory 
data-structures in one file instead of multiple files. They are handled 
differently and will be kind of throw away data so we can regenerate it.

I kind of liked it more when component was Summary because InMemoryData doesn't 
really tell what is inside. Please rename SegmentedFile serialize/deserialize 
to something like serializeBounds/deserializeBounds.

bq. I do see Keycache working in my tests... 

Sorry I wasn't clear when I was saying that. It seems like that summary 
save/load is pointless in it's current form because even if we have loaded 
summary from disk we would anyway have to loop through *whole* PRIMARY_INDEX if 
pre-cache (which is always enabled by default) or re-create-BloomFilter was 
enabled, which is practically means that we spend the same time on I/O there as 
ibuilder.deserialize and dbuilder.deserialize together. We would need to change 
the logic in SSTableReader.load(boolean, Set<DecoratedKey>) the way it doesn't 
have such I/O overhead because this will make it even slower comparing to the 
time it takes now.

                
> Saving IndexSummaries to disk
> -----------------------------
>
>                 Key: CASSANDRA-2392
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2392
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Chris Goffinet
>            Assignee: Vijay
>            Priority: Minor
>             Fix For: 1.1
>
>         Attachments: 0001-re-factor-first-and-last.patch, 
> 0001-save-summaries-to-disk.patch, 0002-save-summaries-to-disk-v2.patch, 
> 0002-save-summaries-to-disk.patch
>
>
> For nodes with millions of keys, doing rolling restarts that take over 10 
> minutes per node can be painful if you have 100 node cluster. All of our time 
> is spent on doing index summary computations on startup. It would be great if 
> we could save those to disk as well. Our indexes are quite large.

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