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From "Sean Hsuan-Yi Chu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-4477) Wrong Plan (potentially wrong result) if wrapping a query with SELECT * FROM
Date Sat, 05 Mar 2016 00:13:40 GMT
Sean Hsuan-Yi Chu created DRILL-4477:
----------------------------------------

             Summary: Wrong Plan (potentially wrong result) if wrapping a query with SELECT
* FROM
                 Key: DRILL-4477
                 URL: https://issues.apache.org/jira/browse/DRILL-4477
             Project: Apache Drill
          Issue Type: Bug
          Components: Query Planning & Optimization
            Reporter: Sean Hsuan-Yi Chu


For example, a query  
{code}
select * from (select s.name, v.name, v.registration from cp.`tpch/region.parquet` s left
outer join cp.`tpch/nation.parquet` v
on (s.name = v.name) 
where s.age < 30) t 
{code}
gives a plan as below:
{code}
+------+------+
| text | json |
+------+------+
| 00-00    Screen
00-01      Project(name=[$0], name0=[$1], registration=[$2])
00-02        Project(name=[$0], name0=[$0], registration=[$3])
00-03          Project(name=[$2], age=[$3], name0=[$0], registration=[$1])
00-04            HashJoin(condition=[=($2, $0)], joinType=[right])
00-06              Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath [path=classpath:/tpch/nation.parquet]],
selectionRoot=classpath:/tpch/nation.parquet, numFiles=1, usedMetadataFile=false, columns=[`name`,
`registration`]]])
00-05              Project(name0=[$0], age=[$1])
00-07                SelectionVectorRemover
00-08                  Filter(condition=[<($1, 30)])
00-09                    Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath [path=classpath:/tpch/region.parquet]],
selectionRoot=classpath:/tpch/region.parquet, numFiles=1, usedMetadataFile=false, columns=[`name`,
`age`]]])
{code}
In the line 00-02, both name and name0 point at the same incoming column (probably due to
the JOIN CONDITION). 

However. the fact that these two are the JOIN condition does not make a case that they must
be equal since implicit casting might be invoked to perform the JOIN condition.

Interestingly, if the SELECT * FROM wrapper is removed, this bug won't be exposed: 
{code}
select s.name, v.name, v.registration from cp.`tpch/region.parquet` s left outer join cp.`tpch/nation.parquet`
v on (s.name = v.name) 
where s.age < 30
{code}

gives 
{code}
00-00    Screen
00-01      Project(name=[$0], name0=[$1], registration=[$2])
00-02        Project(name=[$2], name0=[$0], registration=[$1])
00-03          HashJoin(condition=[=($2, $0)], joinType=[right])
00-05            Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath [path=classpath:/tpch/nation.parquet]],
selectionRoot=classpath:/tpch/nation.parquet, numFiles=1, usedMetadataFile=false, columns=[`name`,
`registration`]]])
00-04            Project(name0=[$0])
00-06              Project(name=[$0])
00-07                SelectionVectorRemover
00-08                  Filter(condition=[<($1, 30)])
00-09                    Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath [path=classpath:/tpch/region.parquet]],
selectionRoot=classpath:/tpch/region.parquet, numFiles=1, usedMetadataFile=false, columns=[`name`,
`age`]]])
{code}



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