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https://issues.apache.org/jira/browse/FLINK-19196?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jark Wu reopened FLINK-19196:
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> FlinkSQL aggregation function to aggregate array typed column to Map/Multiset
> -----------------------------------------------------------------------------
>
> Key: FLINK-19196
> URL: https://issues.apache.org/jira/browse/FLINK-19196
> Project: Flink
> Issue Type: New Feature
> Components: Table SQL / API
> Affects Versions: 1.11.1
> Reporter: sam lin
> Priority: Major
>
> Hi,
>
> For FlinkSQL, how do I aggregate an array typed column to a Map/Multiset
> type? e.g. Given the source events:
> userID, arr_types
> 1, [a, b]
> 2, [a]
> 1, [b, c]
>
> ```
> SELECT userID, collect_arr(arr_types) FROM src_table GROUP BY userID
> ```
> Using the above SQL could produce results like:
> 1, \{a: 1, b: 2, c:1}
> 2, \{a: 1}
> My question is do we have existing UDF to do that? If not, what is the
> recommended way to achieve this? I'm happy to write a UDF if you could
> provide some code pointers. Thanks in advance!
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