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https://issues.apache.org/jira/browse/SPARK-3569?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14171999#comment-14171999
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Xiangrui Meng commented on SPARK-3569:
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I put the design doc here:
https://docs.google.com/document/d/1RGJgVJhCebnilpL15ODcq0EWBeVjl9ltoHUvosWodPg/edit?usp=sharing
> Add metadata field to StructField
> ---------------------------------
>
> Key: SPARK-3569
> URL: https://issues.apache.org/jira/browse/SPARK-3569
> Project: Spark
> Issue Type: New Feature
> Components: MLlib, SQL
> Reporter: Xiangrui Meng
> Assignee: Xiangrui Meng
>
> Want to add a metadata field to StructField that can be used by other
> applications like ML to embed more information about the column.
> {code}
> case class case class StructField(name: String, dataType: DataType, nullable:
> Boolean, metadata: Map[String, Any] = Map.empty)
> {code}
> For ML, we can store feature information like categorical/continuous, number
> categories, category-to-index map, etc.
> One question is how to carry over the metadata in query execution. For
> example:
> {code}
> val features = schemaRDD.select('features)
> val featuresDesc = features.schema('features).metadata
> {code}
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