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https://issues.apache.org/jira/browse/SPARK-11329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15025141#comment-15025141
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Yin Huai commented on SPARK-11329:
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Are you running Spark 1.5? If so, the plan looks fine. When you call
{{sql(...).count}} the optimizer will optimize the query to avoid of evaluating
{{max}} because it is not needed in the count. We have made a few improvements
in Spark 1.6. So, with Spark 1.6, {{sqlCtx.sql('select id, max(struct(data)) as
max from table group by id ').collect()}} should also use TungstenAggregate.
> Expand Star when creating a struct
> ----------------------------------
>
> Key: SPARK-11329
> URL: https://issues.apache.org/jira/browse/SPARK-11329
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Reporter: Yin Huai
> Assignee: Nong Li
> Fix For: 1.6.0
>
>
> It is pretty common for customers to do regular extractions of update data
> from an external datasource (e.g. mysql or postgres). While this is possible
> today, the syntax is a little onerous. With some small improvements to the
> analyzer I think we could make this much easier.
> Goal: Allow users to execute the following two queries as well as their
> dataframe equivalents
> to find the most recent record for each key
> {{SELECT max(struct(timestamp, *)) as mostRecentRecord GROUP BY key}}
> to unnest the struct from above.
> {{SELECT mostRecentRecord.* FROM data}}
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