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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4589) Reduce planning time for file system partition pruning by reducing filter evaluation overhead
Date Thu, 07 Apr 2016 18:31:26 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4589?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15230778#comment-15230778
] 

ASF GitHub Bot commented on DRILL-4589:
---------------------------------------

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

    https://github.com/apache/drill/pull/468#discussion_r58921685
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/planner/FileSystemPartitionDescriptor.java
---
    @@ -148,13 +139,41 @@ public String getName(int index) {
         return partitionLabel + index;
       }
     
    -  private String getBaseTableLocation() {
    +  protected String getBaseTableLocation() {
         final FormatSelection origSelection = (FormatSelection) table.getSelection();
         return origSelection.getSelection().selectionRoot;
       }
     
       @Override
       protected void createPartitionSublists() {
    +    final Collection<String> fileLocations = getFileLocations();
    +    List<PartitionLocation> locations = new LinkedList<>();
    +
    +    final String selectionRoot = getBaseTableLocation();
    +
    +    HashMap<List<String>, List<PartitionLocation>> dirToFileMap = new
HashMap<>();
    --- End diff --
    
    Can you add a comment here with an example <key, value> pair ?  


> Reduce planning time for file system partition pruning by reducing filter evaluation
overhead
> ---------------------------------------------------------------------------------------------
>
>                 Key: DRILL-4589
>                 URL: https://issues.apache.org/jira/browse/DRILL-4589
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Query Planning & Optimization
>            Reporter: Jinfeng Ni
>            Assignee: Jinfeng Ni
>
> When Drill is used to query hundreds of thousands, or even millions of files organized
into multi-level directories, user typically will provide a partition filter like  : dir0
= something and dir1 = something2 and .. .  
> For such queries, we saw the query planning time could be unacceptable long, due to three
main overheads: 1) to expand and get the list of files, 2) to evaluate the partition filter,
3) to get the metadata, in the case of parquet files for which metadata cache file is not
available. 
> DRILL-2517 targets at the 3rd part of overhead. As a follow-up work after DRILL-2517,
we plan to reduce the filter evaluation overhead. For now, the partition filter evaluation
is applied to file level. In many cases, we saw that the number of leaf subdirectories is
significantly lower than that of files. Since all the files under the same leaf subdirecctory
share the same directory metadata, we should apply the filter evaluation at the leaf subdirectory.
By doing that, we could reduce the cpu overhead to evaluate the filter, and the memory overhead
as well.



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