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https://issues.apache.org/jira/browse/CALCITE-4094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17148262#comment-17148262
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Danny Chen commented on CALCITE-4094:
-------------------------------------
The question is, do you want to impose the Strong policy to UDF ? The one who
writes the function may need to have good knowledge of what a Strong policy
means.
> Allow SqlUserDefinedFunction to define an optional Strong.Policy
> ----------------------------------------------------------------
>
> Key: CALCITE-4094
> URL: https://issues.apache.org/jira/browse/CALCITE-4094
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Ruben Q L
> Assignee: Ruben Q L
> Priority: Major
>
> {{FilterJoinRule}} performs some optimizations based on
> {{RelOptUitl#simplifyJoin}}. Specifically, this part of the code:
> {code}
> if (joinType.generatesNullsOnRight()
> && Strong.isNotTrue(filter, rightBitmap)) {
> joinType = joinType.cancelNullsOnRight();
> }
> {code}
> allows e.g. a LEFT join with a condition on its RHS to be transformed into an
> INNER join, with the condition pushed on its right input.
> In order to achieve this, the utility class {{Strong}} defines a certain
> {{Policy}} map, depending on the {{SqlKind}} of a {{RexNode}} (i.e. depending
> on the filter condition). In case of operators such as {{EQUALS}},
> {{NOT_EQUALS}}, {{LESS_THAN}}, etc, it defines {{Policy.ANY}} (i.e.
> expression is null if and only if at least one of its arguments is null). In
> case of a left join with conditions with this policy on the right-hand-side,
> the join gets simplified by this module because of the nullability of the
> right columns. However, in the case of {{SqlUserDefinedFunction}} the policy
> is the default {{Policy.AS_IS}}, which prevents the simplification from
> happening.
> It is proposed to enrich {{SqlUserDefinedFunction}} with an optional
> {{Strong.Policy}}, and adapt {{Strong#isNull}} so that these functions can
> also benefit from this simplification.
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