lirui-apache commented on PR #6175:
URL: https://github.com/apache/iceberg/pull/6175#issuecomment-1316470746

   @pvary That's a good question. Unfortunately the test case you mentioned 
won't work. I looked into how UGI implements equals/hashCode and found the 
behavior is intentional [1]. Hadoop folks did mention that optimizations could 
be possible for proxy users, but it's not safe to do so on their end because 
UGI instances are mutable [2]. Instead they intend to leave that optimization 
to engines/services who have better knowledge about the UGI instances [3].
   
   There were also reports about the UGI behavior causing memory issues in 
Hadoop FileSystem cache (which also uses UGI in the key) [4][5]. But as we have 
TTL on our cache entries, I guess we're fine in that regard.
   
   What do you think?
   
   [1] https://issues.apache.org/jira/browse/HADOOP-6670
   [2] https://issues.apache.org/jira/browse/HADOOP-12529
   [3] 
https://issues.apache.org/jira/browse/HADOOP-12529?focusedCommentId=14984176&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14984176
   [4] https://issues.apache.org/jira/browse/HIVE-3098
   [5] https://issues.apache.org/jira/browse/YARN-58


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