Dmitry Konstantinov created CASSANDRA-19652:
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Summary: 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
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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