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https://issues.apache.org/jira/browse/FLINK-13433?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16896728#comment-16896728
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Jing Zhang commented on FLINK-13433:
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[~jark] Thanks for reminder me. However when lookup key contains constant
equivalent conditions, such as d.name = LiteralValue, if Literal value is null,
there is still no need to fetch data from LookupableTableSource, right?
> Do not fetch data from LookupableTableSource if the JoinKey in left side of
> LookupJoin contains null value
> ----------------------------------------------------------------------------------------------------------
>
> Key: FLINK-13433
> URL: https://issues.apache.org/jira/browse/FLINK-13433
> Project: Flink
> Issue Type: Task
> Components: Table SQL / Planner
> Affects Versions: 1.9.0, 1.10.0
> Reporter: Jing Zhang
> Assignee: Jing Zhang
> Priority: Minor
>
> For LookupJoin, if joinKey in left side of a LeftOuterJoin/InnerJoin contains
> null values, there is no need to fetch data from `LookupableTableSource`.
> However, we don't shortcut the fetch function under the case at present, the
> correctness of results depends on the `TableFunction` implementation of each
> `LookupableTableSource`.
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