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https://issues.apache.org/jira/browse/HIVE-12465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15024738#comment-15024738
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Jesus Camacho Rodriguez commented on HIVE-12465:
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Sure, I will and update the issue.
> Hive might produce wrong results when (outer) joins are merged
> --------------------------------------------------------------
>
> Key: HIVE-12465
> URL: https://issues.apache.org/jira/browse/HIVE-12465
> Project: Hive
> Issue Type: Bug
> Affects Versions: 1.3.0, 2.0.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Priority: Blocker
> Attachments: HIVE-12465.01.patch, HIVE-12465.02.patch,
> HIVE-12465.patch
>
>
> Consider the following query:
> {noformat}
> select * from
> (select * from tab where tab.key = 0)a
> full outer join
> (select * from tab_part where tab_part.key = 98)b
> join
> tab_part c
> on a.key = b.key and b.key = c.key;
> {noformat}
> Hive should execute the full outer join operation (without ON clause) and
> then the join operation (ON a.key = b.key and b.key = c.key). Instead, it
> merges both joins, generating the following plan:
> {noformat}
> STAGE DEPENDENCIES:
> Stage-1 is a root stage
> Stage-0 depends on stages: Stage-1
> STAGE PLANS:
> Stage: Stage-1
> Map Reduce
> Map Operator Tree:
> TableScan
> alias: tab
> filterExpr: (key = 0) (type: boolean)
> Statistics: Num rows: 242 Data size: 22748 Basic stats: COMPLETE
> Column stats: NONE
> Filter Operator
> predicate: (key = 0) (type: boolean)
> Statistics: Num rows: 121 Data size: 11374 Basic stats:
> COMPLETE Column stats: NONE
> Select Operator
> expressions: 0 (type: int), value (type: string), ds (type:
> string)
> outputColumnNames: _col0, _col1, _col2
> Statistics: Num rows: 121 Data size: 11374 Basic stats:
> COMPLETE Column stats: NONE
> Reduce Output Operator
> key expressions: _col0 (type: int)
> sort order: +
> Map-reduce partition columns: _col0 (type: int)
> Statistics: Num rows: 121 Data size: 11374 Basic stats:
> COMPLETE Column stats: NONE
> value expressions: _col1 (type: string), _col2 (type:
> string)
> TableScan
> alias: tab_part
> filterExpr: (key = 98) (type: boolean)
> Statistics: Num rows: 500 Data size: 47000 Basic stats: COMPLETE
> Column stats: NONE
> Filter Operator
> predicate: (key = 98) (type: boolean)
> Statistics: Num rows: 250 Data size: 23500 Basic stats:
> COMPLETE Column stats: NONE
> Select Operator
> expressions: 98 (type: int), value (type: string), ds (type:
> string)
> outputColumnNames: _col0, _col1, _col2
> Statistics: Num rows: 250 Data size: 23500 Basic stats:
> COMPLETE Column stats: NONE
> Reduce Output Operator
> key expressions: _col0 (type: int)
> sort order: +
> Map-reduce partition columns: _col0 (type: int)
> Statistics: Num rows: 250 Data size: 23500 Basic stats:
> COMPLETE Column stats: NONE
> value expressions: _col1 (type: string), _col2 (type:
> string)
> TableScan
> alias: c
> Statistics: Num rows: 500 Data size: 47000 Basic stats: COMPLETE
> Column stats: NONE
> Reduce Output Operator
> key expressions: key (type: int)
> sort order: +
> Map-reduce partition columns: key (type: int)
> Statistics: Num rows: 500 Data size: 47000 Basic stats:
> COMPLETE Column stats: NONE
> value expressions: value (type: string), ds (type: string)
> Reduce Operator Tree:
> Join Operator
> condition map:
> Outer Join 0 to 1
> Inner Join 1 to 2
> keys:
> 0 _col0 (type: int)
> 1 _col0 (type: int)
> 2 key (type: int)
> outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6,
> _col7, _col8
> Statistics: Num rows: 1100 Data size: 103400 Basic stats: COMPLETE
> Column stats: NONE
> File Output Operator
> compressed: false
> Statistics: Num rows: 1100 Data size: 103400 Basic stats:
> COMPLETE Column stats: NONE
> table:
> input format: org.apache.hadoop.mapred.TextInputFormat
> output format:
> org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat
> serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe
> Stage: Stage-0
> Fetch Operator
> limit: -1
> Processor Tree:
> ListSink
> {noformat}
> That plan is equivalent to the following query, which is different than the
> original one:
> {noformat}
> select * from
> (select * from tab where tab.key = 0)a
> full outer join
> (select * from tab_part where tab_part.key = 98)b
> on a.key = b.key
> join
> tab_part c
> on b.key = c.key;
> {noformat}
> It seems to be a problem in the recognition of join operations that can be
> merged into a single multijoin operator.
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