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https://issues.apache.org/jira/browse/HIVE-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13875991#comment-13875991
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Ashutosh Chauhan commented on HIVE-5771:
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Pretty good work, Ted. Hive is in need of this optimization for long time.
Thanks for taking it up.
I scanned the patch. Mostly looking at .q.out changes. Most of them look are
correct, except following :
* smb_mapjoin_18.q : Seems like a Map only job has turned into MR job.
* smb_mapjoin_25.q : extra MR stage got introduced
groupby_sort_1.q --> extra MR stage got introduced
groupby_sort_skew_1.q --> extra MR stage got introduced
udf_between.q --> betweeen 2 and '3' got optimized away. Here types don't
match, shouldn't this instead have optimized into always false filter?
decimal.q - optimization is turned off. Any particular reason?
pcr.q - optimization is turned off. Any particular reason?
I haven't looked at code changes yet. Will be looking at those soon.
> 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-5771.2.patch, HIVE-5771.3.patch,
> HIVE-5771.4.patch, HIVE-5771.5.patch, HIVE-5771.6.patch, HIVE-5771.patch
>
>
> 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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