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https://issues.apache.org/jira/browse/SPARK-16203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15349737#comment-15349737
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Herman van Hovell commented on SPARK-16203:
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I do agree that this is not efficient, but we cannot change the return type of
{{regexp_extract}}.
You could start by writing your own UDF; which can return an array of strings.
Also consider using {{Dataset.explode(...)/Dataset.flatmap(...)}}. A more
advanced approach would be to implement your own {{Expression}}.
> regexp_extract to return an ArrayType(StringType())
> ---------------------------------------------------
>
> Key: SPARK-16203
> URL: https://issues.apache.org/jira/browse/SPARK-16203
> Project: Spark
> Issue Type: Improvement
> Components: PySpark
> Affects Versions: 2.0.0
> Reporter: Max Moroz
> Priority: Minor
>
> regexp_extract only returns a single matched group. If (as if often the case
> - e.g., web log parsing) we need to parse the entire line and get all the
> groups, we'll need to call it as many times as there are groups.
> It's only a minor annoyance syntactically.
> But unless I misunderstand something, it would be very inefficient. (How
> would Spark know not to do multiple pattern matching operations, when only
> one is needed? Or does the optimizer actually check whether the patterns are
> identical, and if they are, avoid the repeated regex matching operations??)
> Would it be possible to have it return an array when the index is not
> specified (defaulting to None)?
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