[jira] [Resolved] (IMPALA-10147) Avoid getting a file handle for data cache hits

["Riza Suminto (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-10147?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Riza Suminto resolved IMPALA-10147.
-----------------------------------
    Fix Version/s: Impala 4.0
       Resolution: Fixed

Closing this Jira as the patch has been merged.

> Avoid getting a file handle for data cache hits
> -----------------------------------------------
>
>                 Key: IMPALA-10147
>                 URL: https://issues.apache.org/jira/browse/IMPALA-10147
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>    Affects Versions: Impala 4.0
>            Reporter: Joe McDonnell
>            Assignee: Riza Suminto
>            Priority: Critical
>             Fix For: Impala 4.0
>
>
> When reading from the data cache, the DiskIo thread first gets a file handle, then it checks the data cache for a hit. If there is a cache hit, then the file handle is not actually used. It is only used if there is a cache miss. There is no real reason to have the file handle open for cache hits. It doesn't really serve any additional purpose, and it adds overhead to cache hits.
> For platforms that do not have the file handle cache, this can be a significant overhead.
> We should only open the file handle after we have checked the data cache and know that we need to read from regular storage.



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