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From "Chris Westin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-2010) merge join returns wrong number of rows with large dataset
Date Mon, 22 Jun 2015 17:59:00 GMT

    [ https://issues.apache.org/jira/browse/DRILL-2010?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14596332#comment-14596332
] 

Chris Westin commented on DRILL-2010:
-------------------------------------

[~vkorukanti]: Until the re-implementation is done, can we at least detect that condition,
and throw an exception?

> merge join returns wrong number of rows with large dataset
> ----------------------------------------------------------
>
>                 Key: DRILL-2010
>                 URL: https://issues.apache.org/jira/browse/DRILL-2010
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Execution - Relational Operators
>    Affects Versions: 0.8.0
>            Reporter: Chun Chang
>            Assignee: Venki Korukanti
>            Priority: Critical
>             Fix For: 1.2.0
>
>         Attachments: DRILL-2010-1.patch, DRILL-2010-1.patch
>
>
> #Mon Jan 12 18:19:31 EST 2015
> git.commit.id.abbrev=5b012bf
> When data set is big enough (like larger than one batch size), merge join will not returns
the correct number of rows. Hash join returns the correct number of rows. Data can be downloaded
from:
> https://s3.amazonaws.com/apache-drill/files/complex100k.json.gz
> With this dataset, the following query should return 10,000,000. 
> {code}
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> alter session set `planner.enable_mergejoin`
= true;
> +------------+------------+
> |     ok     |  summary   |
> +------------+------------+
> | true       | planner.enable_mergejoin updated. |
> +------------+------------+
> 1 row selected (0.024 seconds)
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> alter session set `planner.enable_hashjoin`
= false;
> +------------+------------+
> |     ok     |  summary   |
> +------------+------------+
> | true       | planner.enable_hashjoin updated. |
> +------------+------------+
> 1 row selected (0.024 seconds)
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> select count(a.id) from `complex100k.json`
a inner join `complex100k.json` b on a.gbyi=b.gbyi;
> +------------+
> |   EXPR$0   |
> +------------+
> | 9046760    |
> +------------+
> 1 row selected (6.205 seconds)
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> alter session set `planner.enable_mergejoin`
= false;
> +------------+------------+
> |     ok     |  summary   |
> +------------+------------+
> | true       | planner.enable_mergejoin updated. |
> +------------+------------+
> 1 row selected (0.026 seconds)
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> alter session set `planner.enable_hashjoin`
= true;
> +------------+------------+
> |     ok     |  summary   |
> +------------+------------+
> | true       | planner.enable_hashjoin updated. |
> +------------+------------+
> 1 row selected (0.024 seconds)
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> select count(a.id) from `complex100k.json`
a inner join `complex100k.json` b on a.gbyi=b.gbyi;
> +------------+
> |   EXPR$0   |
> +------------+
> | 10000000   |
> +------------+
> 1 row selected (4.453 seconds)
> {code}
> With smaller dataset, both merge and hash join returns the same correct number.
> physical plan for merge join:
> {code}
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> explain plan for select count(a.id)
from `complex100k.json` a inner join `complex100k.json` b on a.gbyi=b.gbyi;
> +------------+------------+
> |    text    |    json    |
> +------------+------------+
> | 00-00    Screen
> 00-01      StreamAgg(group=[{}], EXPR$0=[COUNT($0)])
> 00-02        Project(id=[$1])
> 00-03          MergeJoin(condition=[=($0, $2)], joinType=[inner])
> 00-05            SelectionVectorRemover
> 00-07              Sort(sort0=[$0], dir0=[ASC])
> 00-09                Scan(groupscan=[EasyGroupScan [selectionRoot=/drill/testdata/complex_type/json/complex100k.json,
numFiles=1, columns=[`gbyi`, `id`], files=[maprfs:/drill/testdata/complex_type/json/complex100k.json]]])
> 00-04            Project(gbyi0=[$0])
> 00-06              SelectionVectorRemover
> 00-08                Sort(sort0=[$0], dir0=[ASC])
> 00-10                  Scan(groupscan=[EasyGroupScan [selectionRoot=/drill/testdata/complex_type/json/complex100k.json,
numFiles=1, columns=[`gbyi`], files=[maprfs:/drill/testdata/complex_type/json/complex100k.json]]])
> {code}



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