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https://issues.apache.org/jira/browse/HIVE-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13824275#comment-13824275
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Eric Hanson commented on HIVE-5771:
-----------------------------------
Ted,
This looks excellent. Please address my comments on ReviewBoard. They are
mostly suggestions about code comments and style. This patch will definitely
help more queries vectorize and reduce some work needed for the translation
from a standard expression to a VectorExpression.
One thing you may want to think about is that right now there is no such thing
as a Timestamp literal, I don't think. But you will create Timestamp constants
in your folding. I don't think that will cause any problems, but it might. It
is something to think about. E.g. do you need an test that casts a string to a
timestamp?
Eric
> 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.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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