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https://issues.apache.org/jira/browse/FLINK-24050?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17406632#comment-17406632
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Jark Wu commented on FLINK-24050:
---------------------------------
Sounds good to me. From my perspective, metadata columns are also some-kind
physical column.
> Support primary keys on metadata columns
> ----------------------------------------
>
> Key: FLINK-24050
> URL: https://issues.apache.org/jira/browse/FLINK-24050
> Project: Flink
> Issue Type: Improvement
> Components: Table SQL / API
> Reporter: Ingo Bürk
> Priority: Major
>
> Currently, primary keys are required to consist solely of physical columns.
> However, there might be scenarios where the actual payload/records do not
> contain a suitable primary key, but a unique identifier is available through
> metadata. In this case it would make sense to define the primary key on such
> a metadata column:
> {code:java}
> CREATE TABLE T (
> uid METADATA,
> content STRING
> PRIMARY KEY (uid) NOT ENFORCED
> ) WITH (…)
> {code}
> A simple example for this would be IMAP: there is nothing unique about any
> single email as a record, but each email in a specific folder on an IMAP
> server has a unique UID (I'm excluding some irrelevant technical details
> here).
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