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Posted to notifications@asterixdb.apache.org by "Till (JIRA)" <ji...@apache.org> on 2018/03/14 23:22:00 UTC

[jira] [Updated] (ASTERIXDB-2252) Improve scan efficiency of LSM components

     [ https://issues.apache.org/jira/browse/ASTERIXDB-2252?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Till updated ASTERIXDB-2252:
----------------------------
    Labels: triaged  (was: )

> 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
>            Priority: Major
>              Labels: triaged
>
> 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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