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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4287) Do lazy reading of parquet metadata cache file
Date Wed, 17 Feb 2016 07:30:18 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15150037#comment-15150037
] 

ASF GitHub Bot commented on DRILL-4287:
---------------------------------------

Github user amansinha100 commented on the pull request:

    https://github.com/apache/drill/pull/376#issuecomment-185074140
  
    Simplified the state management in FileSelection.  @jacques-n is this close enough to
what you intended ?  Also, want to note that this JIRA is motivated by a performance enhancement,
so I haven't added a new unit test.  


> Do lazy reading of parquet metadata cache file
> ----------------------------------------------
>
>                 Key: DRILL-4287
>                 URL: https://issues.apache.org/jira/browse/DRILL-4287
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Query Planning & Optimization
>    Affects Versions: 1.4.0
>            Reporter: Aman Sinha
>            Assignee: Jinfeng Ni
>
> Currently, the parquet metadata cache file is read eagerly during creation of the DrillTable
(as part of ParquetFormatMatcher.isReadable()).  This is not desirable from performance standpoint
since there are scenarios where we want to do some up-front optimizations - e.g. directory-based
partition pruning (see DRILL-2517) or potential limit 0 optimization etc. - and in such situations
it is better to do lazy reading of the metadata cache file.   
> This is a placeholder to perform such delayed reading since it is needed for the aforementioned
optimizations.  



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