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https://issues.apache.org/jira/browse/HIVE-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14047377#comment-14047377
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Ashutosh Chauhan commented on HIVE-5771:
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Yeah, turned out HIVE-7232 was unrelated. Sorry for the confusion.
Yes, extra {{is null}} predicate is introduced by query rewrite involving exist
in clause. You can found more info about this rewrite in design doc uploaded on
HIVE-784
> Constant propagation optimizer for Hive
> ---------------------------------------
>
> Key: HIVE-5771
> URL: https://issues.apache.org/jira/browse/HIVE-5771
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Ted Xu
> Assignee: Ted Xu
> Attachments: HIVE-5771.1.patch, HIVE-5771.10.patch,
> HIVE-5771.11.patch, HIVE-5771.12.patch, HIVE-5771.2.patch, HIVE-5771.3.patch,
> HIVE-5771.4.patch, HIVE-5771.5.patch, HIVE-5771.6.patch, HIVE-5771.7.patch,
> HIVE-5771.8.patch, HIVE-5771.9.patch, HIVE-5771.patch,
> HIVE-5771.patch.javaonly
>
>
> Currently there is no constant folding/propagation optimizer, all expressions
> are evaluated at runtime.
> HIVE-2470 did a great job on evaluating constants on UDF initializing phase,
> however, it is still a runtime evaluation and it doesn't propagate constants
> from a subquery to outside.
> It may reduce I/O and accelerate process if we introduce such an optimizer.
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