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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 Mon, 15 Feb 2016 02:32:18 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15146849#comment-15146849
] 

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

Github user jacques-n commented on a diff in the pull request:

    https://github.com/apache/drill/pull/376#discussion_r52854912
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/FileSelection.java
---
    @@ -45,6 +48,10 @@
       public List<String> files;
       public final String selectionRoot;
     
    +  private boolean checkedForDirectories = false; // whether we have already checked for
directories
    --- End diff --
    
    Can we move from three separate boolean states to one state enumeration?


> 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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