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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 Tue, 02 Feb 2016 06:16:39 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15127739#comment-15127739
] 

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

Github user amansinha100 commented on a diff in the pull request:

    https://github.com/apache/drill/pull/345#discussion_r51528367
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/FileSelection.java
---
    @@ -118,13 +133,34 @@ public boolean apply(@Nullable FileStatus status) {
           }
         }));
     
    -    return create(nonDirectories, null, selectionRoot);
    +    final FileSelection fileSel = create(nonDirectories, null, selectionRoot);
    --- End diff --
    
    I did not change the existing create() call .. it was passing null for the list of files.
 I think it is ok because FileStatus contains the Path which reflects the file name.  It also
seems that if either the list of files is null or the list of statuses is null, the functions
getFiles() or getStatuses() can compute them on the first invocation and save for future use.
 


> 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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