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From "Chen Luo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ASTERIXDB-2252) Improve scan efficiency of LSM components
Date Thu, 18 Jan 2018 01:28:00 GMT
Chen Luo created ASTERIXDB-2252:
-----------------------------------

             Summary: Improve scan efficiency of LSM components
                 Key: ASTERIXDB-2252
                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-2252
             Project: Apache AsterixDB
          Issue Type: Improvement
          Components: STO - Storage
            Reporter: Chen Luo
            Assignee: Chen Luo


The current (full) scan on LSM components is not very efficient, especially on hard disks,
in two aspects:
 # We often need to use a priority queue to merge results from multiple components. However,
we only read a page at a time, which incurs a lot of random I/O overhead on hard disks.
 # Full scan can often fill up (and clean up) the buffer cache. This problem is especially
notable when we do merge. After a merge operation, the buffer cache would be filled up pages
of old components, which would not be accessed by future queries.



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