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https://issues.apache.org/jira/browse/CASSANDRA-19652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17860868#comment-17860868
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Dmitry Konstantinov commented on CASSANDRA-19652:
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The initial version of the optimization:
https://github.com/netudima/cassandra/commit/ef66ff9aac5d6613e3cada89edcaa9bec8e46ad8
> ShallowInfoRetriever: cache offsets to void resetting of RandomAccessReader
> buffer
> ----------------------------------------------------------------------------------
>
> Key: CASSANDRA-19652
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19652
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/SSTable
> Reporter: Dmitry Konstantinov
> Assignee: Dmitry Konstantinov
> Priority: Normal
> Fix For: 5.x
>
>
> Currently in
> org.apache.cassandra.io.sstable.format.big.RowIndexEntry.ShallowInfoRetriever#fetchIndex
> we do 2 seek/read operations: 1st is to find the offset for IndexInfo and
> the 2nd to read it. These are two quite distant regions of the file and for
> standard disk access mode we do not use a benefit from a buffer in
> RandomAccessReader due to jumping between the regions and reseting this
> buffer again and again. A possible improvement here can be to read and cache
> N first offsets (to limit the amount of memory to use) on the first read and
> do later only sequential reads of IndexInfo data. By caching of less than 1Kb
> we can reduce the number of syscalls even more, in my case: from few hundred
> to less than 10.
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