Looks like it's been reported already. It's too bad it's been a year
but should be released into spark 3:
https://issues.apache.org/jira/browse/SPARK-22231
On Fri, Nov 23, 2018 at 8:42 AM Colin Williams
wrote:
>
> Seems like it's worthy of filing a bug against withColumn
>
> On Wed, Nov 21, 2018, 6:25 PM Colin Williams
> >
>> Hello,
>>
>> I'm currently trying to update the schema for a dataframe with nested
>> columns. I would either like to update the schema itself or cast the
>> column without having to explicitly select all the columns just to
>> cast one.
>>
>> In regards to updating the schema it looks like I would probably need
>> to write a more complex map on the schema to find the StructFields I
>> want to update and update them. I haven't found any examples of this
>> but it seems like there should be a simpler way to do it.
>>
>> In regards to changing the column on the dataframe itself, using E.G.
>>
>> val newDF =
>> df.withColumn("existing.top.level.FIELD_NAME",df.col("existing.top.level.FIELD_NAME").cast(LongType))
>>
>> I end up with a new column named "existing.top.level.FIELD_NAME" at
>> the root level vs updating the nested column to the new type. Then has
>> anybody worked out how to both update nested column datatype and also
>> how to update the column type from the nested schema StructType? Are
>> there any easy ways to do this or is there a reason it is not trivial?
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