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https://issues.apache.org/jira/browse/SPARK-21513?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aaron Davidson updated SPARK-21513:
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Labels: Starter (was: )
> SQL to_json should support all column types
> -------------------------------------------
>
> Key: SPARK-21513
> URL: https://issues.apache.org/jira/browse/SPARK-21513
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.2.0
> Reporter: Aaron Davidson
> Labels: Starter
>
> The built-in SQL UDF "to_json" currently supports serializing StructType
> columns, as well as Arrays of StructType columns. If you attempt to use it on
> a different type, for example a map, you get an error like this:
> {code}
> AnalysisException: cannot resolve 'structstojson(`tags`)' due to data type
> mismatch: Input type map<string,string> must be a struct or array of
> structs.;;
> {code}
> This limitation seems arbitrary; if I were to go through the effort of
> enclosing my map in a struct, it would be serializable. Same thing with any
> other non-struct type.
> Therefore the desired improvement is to allow to_json to operate directly on
> any column type. The associated code is
> [here|https://github.com/apache/spark/blob/86174ea89b39a300caaba6baffac70f3dc702788/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala#L653].
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