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https://issues.apache.org/jira/browse/HIVE-860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13904629#comment-13904629
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Jason Dere commented on HIVE-860:
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Does this work for jars on HDFS that have been added using the ADD JAR
functionality? The metastore function work in HIVE-6380 would end up doing
using the same mechanism to add jars from HDFS that would be needed for
metastore UDFs.
So when a non-local jar is added by a session, it gets copied locally to the
session resource directory. But if the local copy of the jar has the same file
name/md5 hash/mtime as what is already saved in the user's distributed cache,
then this should work right?
> Persistent distributed cache
> ----------------------------
>
> Key: HIVE-860
> URL: https://issues.apache.org/jira/browse/HIVE-860
> Project: Hive
> Issue Type: Improvement
> Affects Versions: 0.12.0
> Reporter: Zheng Shao
> Assignee: Brock Noland
> Fix For: 0.13.0
>
> Attachments: HIVE-860.patch, HIVE-860.patch, HIVE-860.patch,
> HIVE-860.patch, HIVE-860.patch
>
>
> DistributedCache is shared across multiple jobs, if the hdfs file name is the
> same.
> We need to make sure Hive put the same file into the same location every time
> and do not overwrite if the file content is the same.
> We can achieve 2 different results:
> A1. Files added with the same name, timestamp, and md5 in the same session
> will have a single copy in distributed cache.
> A2. Filed added with the same name, timestamp, and md5 will have a single
> copy in distributed cache.
> A2 has a bigger benefit in sharing but may raise a question on when Hive
> should clean it up in hdfs.
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