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https://issues.apache.org/jira/browse/CALCITE-6648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17893706#comment-17893706
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Yash Mayya commented on CALCITE-6648:
-------------------------------------
[~mbudiu] I'd be happy to if someone more familiar with Calcite could point me
in the right direction. Based on these snippets -
[https://github.com/apache/calcite/blob/9b4eff06d6a16b3013f01d5fe4bceeaff6822603/core/src/main/java/org/apache/calcite/tools/RelBuilder.java#L4885-L4888,]
[https://github.com/apache/calcite/blob/9b4eff06d6a16b3013f01d5fe4bceeaff6822603/core/src/main/java/org/apache/calcite/sql/fun/SqlFirstLastValueAggFunction.java#L48]
it looks like there is some logic to determine whether a window can be empty
(depending on the window frame bounds) and the return type for {{FIRST_VALUE}}
/ {{LAST_VALUE}} is derived as nullable if the window can be empty. And it
seems like the introduction of the {{SqlNullTreatmentOperator}} is breaking
this logic somewhere.
> IGNORE NULLS / RESPECT NULLS window function option can result in a type
> validation error in SqlToRelConverter
> --------------------------------------------------------------------------------------------------------------
>
> Key: CALCITE-6648
> URL: https://issues.apache.org/jira/browse/CALCITE-6648
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Yash Mayya
> Priority: Major
>
> If the {{IGNORE NULLS}} / {{RESPECT NULLS}} window function option is used
> when the input to the window function is a non-nullable type and the window
> frame is of type {{ROWS}} with an offset based lower or upper bound (i.e.,
> {{{}n PRECEDING / FOLLOWING){}}}, this results in an error
> [here|https://github.com/apache/calcite/blob/9b4eff06d6a16b3013f01d5fe4bceeaff6822603/core/src/main/java/org/apache/calcite/sql2rel/SqlToRelConverter.java#L514-L524]
> - the inferred return type for the window function from the parsed
> {{SqlNode}} is a non-nullable type but the converted type is nullable (which
> makes sense since the result should be {{null}} for rows where the window
> frame is "out of bounds").
>
> This issue does not occur if any of the following conditions are true:
> * {{IGNORE NULLS}} / {{RESPECT NULLS}} options are not specified because in
> this case the inferred return type for the window function call in the parsed
> {{SqlNode}} is also a nullable type.
> * The input to the window function is a nullable type.
> * Both the window frame bounds are UNBOUNDED PRECEDING / CURRENT ROW /
> UNBOUNDED FOLLOWING
>
> While it likely doesn't make much sense for users to specify these options
> when the window function's input type is non-nullable, it should ideally not
> result in an arcane error like:
> {code:java}
> Caused by: java.lang.AssertionError: Conversion to relational algebra failed
> to preserve datatypes:
> validated type:
> RecordType(... INTEGER NOT NULL EXPR$3) NOT NULL
> converted type:
> RecordType(... INTEGER EXPR$3) NOT NULL){code}
>
>
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