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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4530) Improve metadata cache performance for queries with single partition
Date Fri, 17 Jun 2016 20:04:05 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15336817#comment-15336817
] 

ASF GitHub Bot commented on DRILL-4530:
---------------------------------------

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

    https://github.com/apache/drill/pull/519#discussion_r67567343
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/partition/PruneScanRule.java
---
    @@ -269,13 +283,54 @@ protected void doOnMatch(RelOptRuleCall call, Filter filterRel,
Project projectR
             int recordCount = 0;
             int qualifiedCount = 0;
     
    -        // Inner loop: within each batch iterate over the PartitionLocations
    -        for(PartitionLocation part: partitions){
    -          if(!output.getAccessor().isNull(recordCount) && output.getAccessor().get(recordCount)
== 1){
    -            newPartitions.add(part);
    -            qualifiedCount++;
    +        if (checkForSingle &&
    +            partitions.get(0).isCompositePartition() /* apply single partition check
only for composite partitions */) {
    +          // Inner loop: within each batch iterate over the PartitionLocations
    +          for (PartitionLocation part : partitions) {
    --- End diff --
    
    Do you think it's possible to refactor this part of code such that only file system prune
scan will have this logic?  This simplePartition optimization only applies to file system
prune. Also, doOnMatch() method is getting bigger. Something like:  descriptor has supportsSinglePartOptimization(),
and prune scan rule has doSinglePartOpt(), which is by default a no-op, and has implementation
for file system prune rule.
     


> Improve metadata cache performance for queries with single partition 
> ---------------------------------------------------------------------
>
>                 Key: DRILL-4530
>                 URL: https://issues.apache.org/jira/browse/DRILL-4530
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Query Planning & Optimization
>    Affects Versions: 1.6.0
>            Reporter: Aman Sinha
>            Assignee: Aman Sinha
>             Fix For: 1.7.0
>
>
> Consider two types of queries which are run with Parquet metadata caching: 
> {noformat}
> query 1:
> SELECT col FROM  `A/B/C`;
> query 2:
> SELECT col FROM `A` WHERE dir0 = 'B' AND dir1 = 'C';
> {noformat}
> For a certain dataset, the query1 elapsed time is 1 sec whereas query2 elapsed time is
9 sec even though both are accessing the same amount of data.  The user expectation is that
they should perform roughly the same.  The main difference comes from reading the bigger metadata
cache file at the root level 'A' for query2 and then applying the partitioning filter.  query1
reads a much smaller metadata cache file at the subdirectory level. 



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