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https://issues.apache.org/jira/browse/IMPALA-9242?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17004374#comment-17004374
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ASF subversion and git services commented on IMPALA-9242:
---------------------------------------------------------

Commit 05dfb208ff32d434399cb18219425467b0f9b2a9 in impala's branch 
refs/heads/master from xuzhou
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=05dfb20 ]

IMPALA-9195: Using multithreaded execution to accelerate 'show tables/databases'

If Sentry authorization is enabled, users with multi group-policies
will take time to get the result of 'show tables/databases'. It seems
that ResourceAuthorizationProvider.hasAccess performs bad for users
with complex group-policies, IMPALA-9242 will target to address this
problem.

This patch provides a config option 'num_check_authorization_threads' to
accelerate 'show tables/databases' by using multithreading. This configuration
is applicable only when authorization is enabled. A value of 1 disables
multi-threaded execution for checking access. However, a small value of larger
than 1 may limit the parallism of FE requests when checking authorization with
a high concurrency. The value must be in the range of 1 to 128. The default
value of 'num_check_access_threads' is 1.

Change-Id: I860e0d18afa0421665f8b3b1c5561d6bdacc5e96
Reviewed-on: http://gerrit.cloudera.org:8080/14846
Reviewed-by: Impala Public Jenkins <[email protected]>
Tested-by: Impala Public Jenkins <[email protected]>


> Access check should only check against the privileges of the authorizable
> -------------------------------------------------------------------------
>
>                 Key: IMPALA-9242
>                 URL: https://issues.apache.org/jira/browse/IMPALA-9242
>             Project: IMPALA
>          Issue Type: Improvement
>            Reporter: Vihang Karajgaonkar
>            Priority: Major
>
> Currently, according to the implementation of 
> https://github.com/apache/sentry/blob/branch-2.1.0/sentry-provider/sentry-provider-cache/src/main/java/org/apache/sentry/provider/cache/SimpleCacheProviderBackend.java#L64
> each access check request in Sentry is done against all the privileges of the 
> user. Instead, we can reduce the number of privilege checks significantly, if 
> we use this API in 
> https://github.com/apache/sentry/blob/master/sentry-provider/sentry-provider-cache/src/main/java/org/apache/sentry/provider/cache/PrivilegeCache.java#L46
> Unfortunately, SENTRY-1291 which is merged in master branch of Sentry is 
> unavailable. However, if we can have a interface side changes in 
> PrivilegeCache, Impala can implement a prefix-tree based {{PrivilegeCache}} 
> so that number of privileges returned are only related to the given 
> authorizable. This API can then be used in SimpleCacheProviderBackend to 
> reduce the processing time required to check access for a large number of 
> objects in large setups.



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