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https://issues.apache.org/jira/browse/CALCITE-6451?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated CALCITE-6451:
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Labels: pull-request-available (was: )
> Improve Nullability Derivation for Intersect and Minus
> ------------------------------------------------------
>
> Key: CALCITE-6451
> URL: https://issues.apache.org/jira/browse/CALCITE-6451
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Victor Barua
> Assignee: Victor Barua
> Priority: Minor
> Labels: pull-request-available
>
> SetOp overrides `deriveRowType()` and computes the output row type to be the
> least restrictive across all inputs
> [here|https://github.com/apache/calcite/blob/8ab0b03326730aa2cc6b476b2cbd8f99799bdacb/core/src/main/java/org/apache/calcite/rel/core/SetOp.java#L116-L127].
>
> So for example given
> {code:java}
> Input 1: (I64, I64, I64?, I64?)
> Input 2: (I64, I64?, I64, I64?) {code}
> where ? denotes nullable, the least restrictive output computes:
> {code:java}
> Output: (I64, I64?, I64?, I64?) {code}
> For UNION operations, these nullabilities are accurate.
> However for MINUS and INTERSECT there is room for improvement.
> *MINUS* only returns rows from the first input, as such its output
> nullability should always match that of its first input:
> {code:java}
> Output: (I64, I64, I64?, I64?) {code}
> *INTERSECT* only returns rows that match across all inputs. If a column is
> not nullable in any of the inputs, then it is not nullable in the output
> because no rows can be emitted in which that column is null:
> {code:java}
> Output: (I64, I64, I64, I64?) {code}
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