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https://issues.apache.org/jira/browse/FLINK-16679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17336269#comment-17336269
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Flink Jira Bot commented on FLINK-16679:
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This issue was labeled "stale-major" 7 ago and has not received any updates so
it is being deprioritized. If this ticket is actually Major, please raise the
priority and ask a committer to assign you the issue or revive the public
discussion.
> Investigate more efficient outer join plans
> -------------------------------------------
>
> Key: FLINK-16679
> URL: https://issues.apache.org/jira/browse/FLINK-16679
> Project: Flink
> Issue Type: Improvement
> Components: Table SQL / Planner
> Reporter: Timo Walther
> Priority: Major
> Labels: stale-major
>
> FLINK-16344 avoids errors due to incompatible types during planning by
> preserving the nullability attributes of nested types. It added an additional
> check for {{rt.getStructKind == StructKind.PEEK_FIELDS_NO_EXPAND}} to only
> cover nested rows. Not top-level rows. But it seems that a couple of
> execution plans would look nicer if the nullability property is preserved for
> top-level rows as well. However, a lot of join tests fail we should
> investigate this issue if we would like to have more efficient execution
> plans.
> The comment in {{RelDataTypeFactoryImpl#createTypeWithNullability}} says:
> {code}
> According to the SQL standard, nullability for struct types can be defined
> only for columns, which translates to top level structs. Nested struct
> attributes are always nullable, so in principle we could always set the
> nested attributes to be nullable.
> {code}
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