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Posted to issues@spark.apache.org by "Kevin Wallimann (Jira)" <ji...@apache.org> on 2022/01/19 11:50:00 UTC

[jira] [Updated] (SPARK-34805) PySpark loses metadata in DataFrame fields when selecting nested columns

     [ https://issues.apache.org/jira/browse/SPARK-34805?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kevin Wallimann updated SPARK-34805:
------------------------------------
    Attachment: nested_columns_metadata.scala

> PySpark loses metadata in DataFrame fields when selecting nested columns
> ------------------------------------------------------------------------
>
>                 Key: SPARK-34805
>                 URL: https://issues.apache.org/jira/browse/SPARK-34805
>             Project: Spark
>          Issue Type: Bug
>          Components: PySpark
>    Affects Versions: 3.0.1, 3.1.1
>            Reporter: Mark Ressler
>            Priority: Major
>         Attachments: jsonMetadataTest.py, nested_columns_metadata.scala
>
>
> For a DataFrame schema with nested StructTypes, where metadata is set for fields in the schema, that metadata is lost when a DataFrame selects nested fields.  For example, suppose
> {code:java}
> df.schema.fields[0].dataType.fields[0].metadata
> {code}
> returns a non-empty dictionary, then
> {code:java}
> df.select('Field0.SubField0').schema.fields[0].metadata{code}
> returns an empty dictionary, where "Field0" is the name of the first field in the DataFrame and "SubField0" is the name of the first nested field under "Field0".
>  



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