[
https://issues.apache.org/jira/browse/CALCITE-3845?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Chunwei Lei resolved CALCITE-3845.
----------------------------------
Fix Version/s: 1.23.0
Resolution: Fixed
Fixed in
[https://github.com/apache/calcite/commit/ad8cf7e0e96137c40103e0e83539b59e43513b17].
> CASE WHEN expression with nullability CAST is considered as reduced wrongly
> in ReduceExpressionsRule
> ----------------------------------------------------------------------------------------------------
>
> Key: CALCITE-3845
> URL: https://issues.apache.org/jira/browse/CALCITE-3845
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Chunwei Lei
> Assignee: Chunwei Lei
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.23.0
>
> Time Spent: 1h 20m
> Remaining Estimate: 0h
>
> After ReduceExpressionsRule#reduceExpressionsInternal()[1],
> {code:java}
> CAST(CASE WHEN x then true WHEN y then TRUE ELSE false): boolean nullable
> (exp1)
> {code}
> will be changed to
> {code:java}
> WHEN x then CAST(true): boolean nullable WHEN y then CAST(true): boolean
> nullable ELSE CAST(false): boolean nullable. (exp2){code}
> Then exp1 is considered as reduced. In the next step, by
> ReduceExpressionsRule#simplifyPreservingType()[2], exp2 will be changed to
> {code:java}
> CAST(CASE WHEN x then true WHEN y then TRUE ELSE false): boolean nullable
> (exp3)
> {code}
> , which is exactly the same as exp1.
> Though exp1 is actually not reduced, it is still considered as reduced[3],
> which leads to CannotPlanException because of setImportance(project, 0.0)[4].
>
> [1][https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/rules/ReduceExpressionsRule.java#L618]
> [2][https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/rules/ReduceExpressionsRule.java#L624]
>
> [3][https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/rules/ReduceExpressionsRule.java#L303]
>
> [4][https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/rules/ReduceExpressionsRule.java#L312]
>
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