Padma Penumarthy created DRILL-4990:
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             Summary: Use new HDFS API access instead of listStatus to check if 
users have permissions to access workspace.
                 Key: DRILL-4990
                 URL: https://issues.apache.org/jira/browse/DRILL-4990
             Project: Apache Drill
          Issue Type: Bug
          Components: Query Planning & Optimization
    Affects Versions: 1.8.0
            Reporter: Padma Penumarthy
            Assignee: Padma Penumarthy
             Fix For: 1.9.0


For every query, we build the schema tree 
(runSQL->getPlan->getNewDefaultSchema->getRootSchema). All workspaces in all 
storage plugins are checked and are added to the schema tree if they are 
accessible by the user who initiated the query.  For file system plugin, 
listStatus API is used to check if  the workspace is accessible or not 
(WorkspaceSchemaFactory.accessible) by the user.  The idea seem to be if the 
user does not have access to file(s) in the workspace, listStatus will generate 
an exception and we return false. But, listStatus (which lists all the entries 
of a directory) is an expensive operation when there are large number of files 
in the directory. A new API is added in Hadoop 2.6 called access (HDFS-6570) 
which provides the ability to check if the user has permissions on a 
file/directory.  Use this new API instead of listStatus. For a directory with 
256k+ files, an improvement of upto 10 sec in planning time was observed when 
using the new API vs. old way of listStatus. 



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