Ruben Q L created CALCITE-4094:
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Summary: 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
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 conditions pushed on its right input.
In order to achieve this, the utility class {{Strong}} defines a certain
{{Policy}} map, depending on the {{SqlKind}} of the {{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 for these ones 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 optimization.
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