[jira] [Commented] (IMPALA-8691) Query hint for disabling data caching

["ASF subversion and git services (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IMPALA-8691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16914553#comment-16914553 ] 

ASF subversion and git services commented on IMPALA-8691:
---------------------------------------------------------

Commit 9874ce37a989240571e2473dce3153357a0e417f in impala's branch refs/heads/master from Michael Ho
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=9874ce3 ]

IMPALA-8691: Query option to disable data cache

This change adds a query option to disable the data cache for
a given session. By default, this option is set to false. When
it's set to true, all queries will by-pass the data cache. This
allows users to avoid polluting the cache for accesses to tables
which they don't want to cache. A follow-up change will add
a per-table query hint to allow caching disabled for a given
table only.

There is some small refactoring in the code to make it clearer
the type of caching being referred to in the code. As the code
stands now, we have both HDFS caching (for local reads) and the
data cache (for remote reads). BufferOpts has been extended to
allow users to explicitly state intention for using either/both
of the caches.

Change-Id: I39122ac38435cedf94b2b39145863764d0b5b6c8
Reviewed-on: http://gerrit.cloudera.org:8080/14015
Reviewed-by: Tim Armstrong <ta...@cloudera.com>
Tested-by: Impala Public Jenkins <im...@cloudera.com>


> Query hint for disabling data caching
> -------------------------------------
>
>                 Key: IMPALA-8691
>                 URL: https://issues.apache.org/jira/browse/IMPALA-8691
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>    Affects Versions: Impala 3.3.0
>            Reporter: Michael Ho
>            Assignee: Michael Ho
>            Priority: Major
>
> IMPALA-8690 tracks the effort for a better eviction algorithm for the Impala's data cache. As a short term workaround, it would be nice to allow users to explicitly set certain tables as not cacheable via query hints or simply disable caching for a query via query options.



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