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https://issues.apache.org/jira/browse/FLINK-5406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15865136#comment-15865136
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ASF GitHub Bot commented on FLINK-5406:
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Github user godfreyhe commented on the issue:
https://github.com/apache/flink/pull/3101
Done, thanks for the suggest @fhueske
> add normalization phase for predicate logical plan rewriting between
> decorrelate query phase and volcano optimization phase
> ---------------------------------------------------------------------------------------------------------------------------
>
> Key: FLINK-5406
> URL: https://issues.apache.org/jira/browse/FLINK-5406
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: godfrey he
> Assignee: godfrey he
>
> Normalization phase is for predicate logical plan rewriting and is
> independent of cost module. The rules in normalization phase do not need to
> repeatedly applied to different logical plan which is different to volcano
> optimization phase. And the benefit of normalization phase is to reduce the
> running time of volcano planner.
> *ReduceExpressionsRule* can apply various simplifying transformations on
> RexNode trees. Currently, there are two transformations:
> 1) Constant reduction, which evaluates constant subtrees, replacing them with
> a corresponding RexLiteral
> 2) Removal of redundant casts, which occurs when the argument into the cast
> is the same as the type of the resulting cast expression
> the above transformations do not depend on the cost module, so we can move
> the rules in *ReduceExpressionsRule* from
> DATASET_OPT_RULES/DATASTREAM_OPT_RULES to DataSet/DataStream Normalization
> Rules.
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