Details

Type: Bug

Status: Closed

Priority: Major

Resolution: Fixed

Affects Version/s: 0.13.0

Fix Version/s: 0.14.0

Component/s: Query Processor

Labels:None
Description
With HIVE 0.13.0, run the following test case:
create table src(key bigint, value string); select count(distinct key) as col0 from src order by col0;
The following exception will be thrown:
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
This issue is related to HIVE6455. When hive.optimize.reducededuplication is set to false, then this issue will be gone.
Logical plan when hive.optimize.reducededuplication=false;
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
You will see that RS_3 and RS_6 are not merged.
Logical plan when hive.optimize.reducededuplication=true;
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
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?
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); } ... }
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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 is related to

HIVE6455 Scalable dynamic partitioning and bucketing optimization
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I am thinking about the following fix, but not sure if right:
sameKeys():
ExprNodeDesc pexpr = pexprs.get;
{ return null; }ExprNodeDesc cexpr = ExprNodeDescUtils.backtrack(cexprs.get, 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))