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https://issues.apache.org/jira/browse/CALCITE-7038?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17979905#comment-17979905
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Christian Beikov commented on CALCITE-7038:
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The requirement seems a bit arbitrary to me, given that the query does not
explicitly order by the {{branchProtectionRules}} array value.
I am trying to integrate external data into Calcite and avoid unnecessary
traversal/conversions as much as possible. SQL databases also have types that
are not comparable and then throw an error when trying to order by such values
e.g. ordering by a BLOB usually is not allowed. Don't you think it's worth
giving this another thought?
On the Java object side, the array is represented as {{java.util.ArrayList}}
and the struct element is a custom java class that I don't necessarily control.
AFAIU, I could simply wrap the array list in a {{FakeComparableList}} to
satisfy the compiler needs, because no comparisons happen, but not sure if the
struct might not become a problem one day as well.
I certainly can workaround this if you say this is how it's supposed to be,
though I think it would be for the better to reconsider in light of integrating
"existing external data".
> EnumerableUncollect unnecessarily assuming fields are Comparable
> ----------------------------------------------------------------
>
> Key: CALCITE-7038
> URL: https://issues.apache.org/jira/browse/CALCITE-7038
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.39.0
> Reporter: Christian Beikov
> Priority: Major
>
> {{EnumerableUncollect}} uses {{JavaRowFormat.LIST}} which unnecessarily
> requires that all the field values are {{Comparable}} leading to a
> {{ClassCastException}} when executing a query like e.g. against data that is
> not fully comparable
> {code:sql}
> select r.id
> from GitHubRepository r
> where not exists (
> select 1
> from unnest(r.branchProtectionRules) as br
> and exists (select 1 from GitHubRepository r)
> )
> {code}
> Assuming {{branchProtectionRules}} is {{Array(Struct(matchingRefs:
> Integer))}}. Note that the {{EXISTS}} predicate in the unnest subquery is
> needed to trigger the failure.
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