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From "Jinfeng Ni (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DRILL-2543) Correlated subquery where outer table contains NULL values returns seemingly wrong result
Date Fri, 10 Jul 2015 00:12:05 GMT

     [ https://issues.apache.org/jira/browse/DRILL-2543?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jinfeng Ni updated DRILL-2543:
------------------------------
    Fix Version/s:     (was: 1.2.0)
                   1.3.0

> Correlated subquery where outer table contains NULL values returns  seemingly wrong result
> ------------------------------------------------------------------------------------------
>
>                 Key: DRILL-2543
>                 URL: https://issues.apache.org/jira/browse/DRILL-2543
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Query Planning & Optimization
>    Affects Versions: 0.8.0
>            Reporter: Victoria Markman
>            Assignee: Jinfeng Ni
>            Priority: Critical
>             Fix For: 1.3.0
>
>
> {code}
> 0: jdbc:drill:schema=dfs> select * from t1;
> +------------+------------+------------+
> |     a1     |     b1     |     c1     |
> +------------+------------+------------+
> | 1          | 2015-03-01 | aaaaa      |
> | 2          | 2015-03-02 | bbbbb      |
> | null       | null       | null       |
> +------------+------------+------------+
> 3 rows selected (0.064 seconds)
> 0: jdbc:drill:schema=dfs> select * from t2;
> +------------+------------+------------+
> |     a2     |     b2     |     c2     |
> +------------+------------+------------+
> | 5          | 2017-03-01 | a          |
> +------------+------------+------------+
> 1 row selected (0.07 seconds)
> 0: jdbc:drill:schema=dfs> select t1.c1, count(*) from t1 where t1.b1 not in (select
b2 from t2 where t1.a1 = t2.a2) group by t1.c1 order by t1.c1;
> +------------+------------+
> |     c1     |   EXPR$1   |
> +------------+------------+
> | aaaaa      | 1          |
> | bbbbb      | 1          |
> +------------+------------+
> 2 rows selected (0.32 seconds)
> {code}
> Postgres returns row from the outer table where a1 is null.
> This is part that I don't understand, because join condition in the subquery should have
eliminated row where a1 IS NULL. To me Drill result looks correct. Unless there is something
different in correlated comparison semantics that I'm not aware of.
> {code}
> postgres=# select * from t1;
>  a1 |     b1     |  c1
> ----+------------+-------
>   1 | 2015-03-01 | aaaaa
>   2 | 2015-03-02 | bbbbb
>     |            |
> (3 rows)
> {code}
> Explain plan for the query:
> {code}
> 00-01      Project(c1=[$0], EXPR$1=[$1])
> 00-02        StreamAgg(group=[{0}], EXPR$1=[COUNT()])
> 00-03          Sort(sort0=[$0], dir0=[ASC])
> 00-04            Project(c1=[$0])
> 00-05              SelectionVectorRemover
> 00-06                Filter(condition=[NOT(IS TRUE($3))])
> 00-07                  HashJoin(condition=[=($1, $2)], joinType=[left])
> 00-09                    Project($f1=[$0], $f3=[$2])
> 00-11                      SelectionVectorRemover
> 00-13                        Filter(condition=[IS NOT NULL($1)])
> 00-15                          Project(c1=[$1], b1=[$0], a1=[$2])
> 00-17                            Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath
[path=maprfs:/test/t1]], selectionRoot=/test/t1, numFiles=1, columns=[`c1`, `b1`, `a1`]]])
> 00-08                    Project($f02=[$1], $f2=[$2])
> 00-10                      StreamAgg(group=[{0, 1}], agg#0=[MIN($2)])
> 00-12                        Sort(sort0=[$0], sort1=[$1], dir0=[ASC], dir1=[ASC])
> 00-14                          Project($f0=[$1], $f02=[$2], $f1=[true])
> 00-16                            HashJoin(condition=[=($2, $0)], joinType=[inner])
> 00-18                              StreamAgg(group=[{0}])
> 00-20                                Sort(sort0=[$0], dir0=[ASC])
> 00-22                                  Project($f0=[$1])
> 00-23                                    SelectionVectorRemover
> 00-24                                      Filter(condition=[IS NOT NULL($0)])
> 00-25                                        Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath
[path=maprfs:/test/t1]], selectionRoot=/test/t1, numFiles=1, columns=[`b1`, `a1`]]])
> 00-19                              Project(a2=[$1], b2=[$0])
> 00-21                                Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath
[path=maprfs:/test/t2]], selectionRoot=/test/t2, numFiles=1, columns=[`a2`, `b2`]]])
> {code}



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