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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 18:29:25 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4589?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15230775#comment-15230775
] 

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_r58921279
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/planner/DFSDirPartitionLocation.java
---
    @@ -0,0 +1,70 @@
    +/**
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + * http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +/**
    + * Class defines a single partition corresponding to a directory in a DFS table.
    + */
    +package org.apache.drill.exec.planner;
    +
    +
    +import com.google.common.collect.Lists;
    +
    +import java.util.Collection;
    +import java.util.List;
    +
    +public class DFSDirPartitionLocation implements PartitionLocation {
    +  private final Collection<PartitionLocation> subPartitions;
    --- End diff --
    
    Can this collection be a mix of directory partition locations as well as file partition
locations ?  It has become a little confusing to keep track of the distinction between the
two since the term PartitionLocation is overloaded.   Can you add appropriate javadoc to clarify
? 


> 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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