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https://issues.apache.org/jira/browse/HIVE-7012?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13988631#comment-13988631
]
Sun Rui commented on HIVE-7012:
-------------------------------
I am thinking about the following fix, but not sure if right:
sameKeys():
ExprNodeDesc pexpr = pexprs.get(i);
ExprNodeDesc cexpr = ExprNodeDescUtils.backtrack(cexprs.get(i), child,
parent);
// check if cexpr is from the parent
if (cexpr == null || (cexpr not contained in the colExprMap of the
parent operator) || !pexpr.isSame(cexpr)) {
return null;
}
> Wrong RS de-duplication in the ReduceSinkDeDuplication Optimizer
> ----------------------------------------------------------------
>
> Key: HIVE-7012
> URL: https://issues.apache.org/jira/browse/HIVE-7012
> Project: Hive
> Issue Type: Bug
> Components: Query Processor
> Affects Versions: 0.13.0
> Reporter: Sun Rui
>
> With HIVE 0.13.0, run the following test case:
> {code:sql}
> create table src(key bigint, value string);
> select
> count(distinct key) as col0
> from src
> order by col0;
> {code}
> The following exception will be thrown:
> {noformat}
> java.lang.RuntimeException: Error in configuring object
> at
> org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:93)
> at
> org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:64)
> at
> org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:117)
> at
> org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:485)
> at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:420)
> at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:396)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1121)
> at org.apache.hadoop.mapred.Child.main(Child.java:249)
> Caused by: java.lang.reflect.InvocationTargetException
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at
> org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:88)
> ... 9 more
> Caused by: java.lang.RuntimeException: Reduce operator initialization failed
> at
> org.apache.hadoop.hive.ql.exec.mr.ExecReducer.configure(ExecReducer.java:173)
> ... 14 more
> Caused by: java.lang.RuntimeException: cannot find field _col0 from
> [0:reducesinkkey0]
> at
> org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorUtils.getStandardStructFieldRef(ObjectInspectorUtils.java:415)
> at
> org.apache.hadoop.hive.serde2.objectinspector.StandardStructObjectInspector.getStructFieldRef(StandardStructObjectInspector.java:150)
> at
> org.apache.hadoop.hive.ql.exec.ExprNodeColumnEvaluator.initialize(ExprNodeColumnEvaluator.java:79)
> at
> org.apache.hadoop.hive.ql.exec.GroupByOperator.initializeOp(GroupByOperator.java:288)
> at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:376)
> at
> org.apache.hadoop.hive.ql.exec.mr.ExecReducer.configure(ExecReducer.java:166)
> ... 14 more
> {noformat}
> This issue is related to HIVE-6455. When hive.optimize.reducededuplication is
> set to false, then this issue will be gone.
> Logical plan when hive.optimize.reducededuplication=false;
> {noformat}
> src
> TableScan (TS_0)
> alias: src
> Statistics: Num rows: 0 Data size: 0 Basic stats: NONE Column stats: NONE
> Select Operator (SEL_1)
> expressions: key (type: bigint)
> outputColumnNames: key
> Statistics: Num rows: 0 Data size: 0 Basic stats: NONE Column stats:
> NONE
> Group By Operator (GBY_2)
> aggregations: count(DISTINCT key)
> keys: key (type: bigint)
> mode: hash
> outputColumnNames: _col0, _col1
> Statistics: Num rows: 0 Data size: 0 Basic stats: NONE Column stats:
> NONE
> Reduce Output Operator (RS_3)
> istinctColumnIndices:
> key expressions: _col0 (type: bigint)
> DistributionKeys: 0
> sort order: +
> OutputKeyColumnNames: _col0
> Statistics: Num rows: 0 Data size: 0 Basic stats: NONE Column
> stats: NONE
> Group By Operator (GBY_4)
> aggregations: count(DISTINCT KEY._col0:0._col0)
> mode: mergepartial
> outputColumnNames: _col0
> Statistics: Num rows: 1 Data size: 16 Basic stats: COMPLETE
> Column stats: NONE
> Select Operator (SEL_5)
> expressions: _col0 (type: bigint)
> outputColumnNames: _col0
> Statistics: Num rows: 1 Data size: 16 Basic stats: COMPLETE
> Column stats: NONE
> Reduce Output Operator (RS_6)
> key expressions: _col0 (type: bigint)
> DistributionKeys: 1
> sort order: +
> OutputKeyColumnNames: reducesinkkey0
> OutputVAlueColumnNames: _col0
> Statistics: Num rows: 1 Data size: 16 Basic stats: COMPLETE
> Column stats: NONE
> value expressions: _col0 (type: bigint)
> Extract (EX_7)
> Statistics: Num rows: 1 Data size: 16 Basic stats: COMPLETE
> Column stats: NONE
> File Output Operator (FS_8)
> compressed: false
> Statistics: Num rows: 1 Data size: 16 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
> {noformat}
> You will see that RS_3 and RS_6 are not merged.
> Logical plan when hive.optimize.reducededuplication=true;
> {noformat}
> src
> TableScan (TS_0)
> alias: src
> Statistics: Num rows: 0 Data size: 0 Basic stats: NONE Column stats: NONE
> Select Operator (SEL_1)
> expressions: key (type: bigint)
> outputColumnNames: key
> Statistics: Num rows: 0 Data size: 0 Basic stats: NONE Column stats:
> NONE
> Group By Operator (GBY_2)
> aggregations: count(DISTINCT key)
> keys: key (type: bigint)
> mode: hash
> outputColumnNames: _col0, _col1
> Statistics: Num rows: 0 Data size: 0 Basic stats: NONE Column stats:
> NONE
> Reduce Output Operator (RS_3)
> istinctColumnIndices:
> key expressions: _col0 (type: bigint)
> DistributionKeys: 1
> sort order: +
> OutputKeyColumnNames: reducesinkkey0
> Statistics: Num rows: 0 Data size: 0 Basic stats: NONE Column
> stats: NONE
> Group By Operator (GBY_4)
> aggregations: count(DISTINCT KEY._col0:0._col0)
> mode: mergepartial
> outputColumnNames: _col0
> Statistics: Num rows: 1 Data size: 16 Basic stats: COMPLETE
> Column stats: NONE
> Select Operator (SEL_5)
> expressions: _col0 (type: bigint)
> outputColumnNames: _col0
> Statistics: Num rows: 1 Data size: 16 Basic stats: COMPLETE
> Column stats: NONE
> File Output Operator (FS_8)
> compressed: false
> Statistics: Num rows: 1 Data size: 16 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
> {noformat}
> You will see that RS_6 has been merged into RS_3. However, Obviously the
> merge is incorrect because RS_3 and RS_6 have different sort keys. (The sort
> key for RS_3 is
> key and the sort key for RS_6 is count(distinct key)).
> The problem is that the method sameKeys() returns the result that both RS
> have same keys. sameKeys() depends ExprNodeDescUtils.backtrack() to backtrack
> a key expr of cRS to pRS.
> I don't understand the logical behind the following logic in
> ExprNodeDescUtils:
> Why still backtrack when there is no mapping for the column of the current
> operator?
> {code}
> private static ExprNodeDesc backtrack(ExprNodeColumnDesc column,
> Operator<?> current,
> Operator<?> terminal) throws SemanticException {
> ...
> if (mapping == null || !mapping.containsKey(column.getColumn())) {
> return backtrack((ExprNodeDesc)column, current, terminal);
> }
> ...
> }
> {code}
> The process of backtracking _col0 of cRS to pRS:
> RS_6:_col0 --> SEL_5:_col0 --> GBY_4:_col0 (because the colExprMap is null
> for GBY_4) --> RS_3:_col0 (No mapping for output column _col0), which is a
> wrong backtrack.
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