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https://issues.apache.org/jira/browse/HIVE-17405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16150009#comment-16150009
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Sahil Takiar commented on HIVE-17405:
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[~lirui] updated patch with better comments. I think the call to constant
propagation was probably originally added just for DPP, but there are benefits
to running it after all the operator optimizations have run in the
{{SparkCompiler}}. Some of the optimizations (such as DPP) may have modified
the operator tree such that additional constants can be propagated.
The modifications to the skew join qtests are one example.
> HoS DPP ConstantPropagate should use ConstantPropagateOption.SHORTCUT
> ---------------------------------------------------------------------
>
> Key: HIVE-17405
> URL: https://issues.apache.org/jira/browse/HIVE-17405
> Project: Hive
> Issue Type: Sub-task
> Components: Spark
> Reporter: Sahil Takiar
> Assignee: Sahil Takiar
> Attachments: HIVE-17405.1.patch, HIVE-17405.2.patch,
> HIVE-17405.3.patch, HIVE-17405.4.patch, HIVE-17405.5.patch,
> HIVE-17405.6.patch, HIVE-17405.7.patch
>
>
> In {{SparkCompiler#runDynamicPartitionPruning}} we should change {{new
> ConstantPropagate().transform(parseContext)}} to {{new
> ConstantPropagate(ConstantPropagateOption.SHORTCUT).transform(parseContext)}}
> Hive-on-Tez does the same thing.
> Running the full constant propagation isn't really necessary, we just want to
> eliminate any {{and true}} predicates that were introduced by
> {{SyntheticJoinPredicate}} and {{DynamicPartitionPruningOptimization}}. The
> {{SyntheticJoinPredicate}} will introduce dummy filter predicates into the
> operator tree, and {{DynamicPartitionPruningOptimization}} will replace them.
> The predicates introduced via {{SyntheticJoinPredicate}} are necessary to
> help {{DynamicPartitionPruningOptimization}} determine if DPP can be used or
> not.
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