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https://issues.apache.org/jira/browse/HIVE-12735?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15068987#comment-15068987
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Ashutosh Chauhan commented on HIVE-12735:
-----------------------------------------
+1 LGTM
> Constant folding for WHEN/CASE expression does not set return type correctly
> ----------------------------------------------------------------------------
>
> Key: HIVE-12735
> URL: https://issues.apache.org/jira/browse/HIVE-12735
> Project: Hive
> Issue Type: Bug
> Components: Logical Optimizer
> Affects Versions: 1.3.0, 2.0.0, 2.1.0
> Reporter: Prasanth Jayachandran
> Assignee: Prasanth Jayachandran
> Attachments: HIVE-12735.1.patch
>
>
> For the following query
> {code}
> SELECT IF ( ( (CASE WHEN bool0 THEN 1 WHEN NOT bool0 THEN 0 END) = (CASE WHEN
> TRUE THEN 1 WHEN NOT TRUE THEN 0 END) ), key0, IF ( ( (CASE WHEN bool0 THEN 1
> WHEN NOT bool0 THEN 0 END) = (CASE WHEN FALSE THEN 1 WHEN NOT FALSE THEN 0
> END) ), key1, key2 ) ) FROM src_orc;
> {code}
> the expression gets constant folded to
> {code}
> if(CASE WHEN (bool0) THEN (true) WHEN ((not bool0)) THEN (false) END, key0,
> if(CASE WHEN (bool0) THEN (false) WHEN ((not bool0)) THEN (true) END, key1,
> key2)) (type: string)
> {code}
> however, the GenericUDFWhen and GenericUDFCase expression retain the original
> return type (int) instead of the folded return type (boolean). This can cause
> ClassCastException for the above query when vectorization is enabled.
> Following is the exception
> {code}
> Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: Error evaluating
> if(CASE WHEN (bool0) THEN (true) WHEN ((not bool0)) THEN (false) END, key0,
> if(CASE WHEN (bool0) THEN (false) WHEN ((not bool0)) THEN (true) END, key1,
> key2))
> at
> org.apache.hadoop.hive.ql.exec.vector.VectorSelectOperator.process(VectorSelectOperator.java:126)
> at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:852)
> at
> org.apache.hadoop.hive.ql.exec.TableScanOperator.process(TableScanOperator.java:114)
> at
> org.apache.hadoop.hive.ql.exec.MapOperator$MapOpCtx.forward(MapOperator.java:168)
> at
> org.apache.hadoop.hive.ql.exec.vector.VectorMapOperator.process(VectorMapOperator.java:45)
> ... 18 more
> Caused by: java.lang.ClassCastException: org.apache.hadoop.io.BooleanWritable
> cannot be cast to org.apache.hadoop.io.IntWritable
> at
> org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableIntObjectInspector.get(WritableIntObjectInspector.java:36)
> at
> org.apache.hadoop.hive.ql.exec.vector.udf.VectorUDFAdaptor.setOutputCol(VectorUDFAdaptor.java:262)
> at
> org.apache.hadoop.hive.ql.exec.vector.udf.VectorUDFAdaptor.setResult(VectorUDFAdaptor.java:210)
> at
> org.apache.hadoop.hive.ql.exec.vector.udf.VectorUDFAdaptor.evaluate(VectorUDFAdaptor.java:140)
> at
> org.apache.hadoop.hive.ql.exec.vector.expressions.VectorExpression.evaluateChildren(VectorExpression.java:121)
> at
> org.apache.hadoop.hive.ql.exec.vector.expressions.IfExprStringGroupColumnStringGroupColumn.evaluate(IfExprStringGroupColumnStringGroupColumn.java:54)
> at
> org.apache.hadoop.hive.ql.exec.vector.VectorSelectOperator.process(VectorSelectOperator.java:123)
> ... 22 more
> {code}
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