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https://issues.apache.org/jira/browse/CALCITE-6228?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated CALCITE-6228:
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Labels: pull-request-available (was: )
> ELEMENT function infers incorrect return type
> ---------------------------------------------
>
> Key: CALCITE-6228
> URL: https://issues.apache.org/jira/browse/CALCITE-6228
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.36.0
> Reporter: Mihai Budiu
> Priority: Minor
> Labels: pull-request-available
>
> The ELEMENT function is defined in the documentation as follows:
> [https://calcite.apache.org/docs/reference.html#collection-functions]
> {quote}Returns the sole element of an array or multiset; null if the
> collection is empty; throws if it has more than one element.
> {quote}
> However, the type inference returns just the type of the element of the
> collection, without changing its nullability.
> The type inference is implemented as follows in SqlStdOperatorTable:
> {code:java}
> public static final SqlFunction ELEMENT =
> SqlBasicFunction.create("ELEMENT",
> ReturnTypes.MULTISET_ELEMENT_NULLABLE,
> OperandTypes.COLLECTION);
> {code}
> However, reading the definition of MULTISET_ELEMENT_NULLABLE in
> ReturnTypes.java:
> {code:java}
> public static final SqlReturnTypeInference MULTISET_ELEMENT_NULLABLE =
> MULTISET.andThen(SqlTypeTransforms.TO_COLLECTION_ELEMENT_TYPE);
> {code}
> we notice that it is not forced to be nullable. Probably the correct
> implementation would be
> {code:java}
> public static final SqlReturnTypeInference MULTISET_ELEMENT_NULLABLE =
> MULTISET.andThen(SqlTypeTransforms.TO_COLLECTION_ELEMENT_TYPE)
> .andThen(SqlTypeTransforms.FORCE_NULLABLE);
> {code}
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