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https://issues.apache.org/jira/browse/HIVE-14431?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15990261#comment-15990261
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Remus Rusanu commented on HIVE-14431:
-------------------------------------
Since the original path from Jesus the simplify rules have moved into Calcite
(RexSimplify). We have to follow up as a Calcite issue, and see if they
desire/accept this rule.
An alternative is to do something similar to the
{{HivePointLookupOptimizerRule}}, ie. have a RelOptRule for Filter/Join
operators and inspect the condition for COALESCE => CASE simplification. This
would be entirely in Hive space.
> Recognize COALESCE as CASE
> --------------------------
>
> Key: HIVE-14431
> URL: https://issues.apache.org/jira/browse/HIVE-14431
> Project: Hive
> Issue Type: Improvement
> Components: CBO
> Affects Versions: 2.2.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Remus Rusanu
> Attachments: HIVE-14431.01.patch, HIVE-14431.2.patch, HIVE-14431.patch
>
>
> Transform:
> {code}
> (COALESCE(a, '') = '') OR
> (a = 'A' AND b = c) OR
> (a = 'B' AND b = d) OR
> (a = 'C' AND b = e) OR
> (a = 'D' AND b = f) OR
> (a = 'E' AND b = g) OR
> (a = 'F' AND b = h)
> {code}
> into:
> {code}
> (a='') OR
> (a is null) OR
> (a = 'A' AND b = c) OR
> (a = 'B' AND b = d) OR
> (a = 'C' AND b = e) OR
> (a = 'D' AND b = f) OR
> (a = 'E' AND b = g) OR
> (a = 'F' AND b = h)
> {code}
> With complex queries, this will lead us to factor more predicates that could
> be pushed to the TS.
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