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From amansinha100 <...@git.apache.org>
Subject [GitHub] drill pull request #519: DRILL-4530: Optimize partition pruning with metadat...
Date Tue, 28 Jun 2016 00:03:53 GMT
Github user amansinha100 commented on a diff in the pull request:

    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/FileSelection.java
    @@ -47,16 +47,25 @@
       private List<FileStatus> statuses;
       public List<String> files;
    +  /**
    +   * root path for the selections
    +   */
       public final String selectionRoot;
    +  /**
    +   * root path for the metadata cache file (if any)
    +   */
    +  public final String cacheFileRoot;
    --- End diff --
    That was my initial approach (updating the selectionRoot without keeping a separate cacheFileRoot).
  However,  I ran into a few issues.  The main one that I recall is that the dir0, dir1 etc
columns are associated with the selectionRoot, so suppose I run the following query: 
        SELECT dir0, dir1 FROM dfs.tmp.t2 WHERE dir0=2015 AND dir1='Q1' 
    and if the selectionRoot gets modified to point to '2015/Q1'  then we have lost the context
of the original dir0, dir1 because everything will become relative to the new selectionRoot.
   This produces wrong results.   The same problem occurred with a SELECT *  query where the
directory columns where not showing up correctly. 

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