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https://issues.apache.org/jira/browse/SPARK-25140?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16583486#comment-16583486
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Kris Mok commented on SPARK-25140:
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Thanks maropu-san! No, I'm not working on this ticket; I'm currently swamped by
other tasks close to a deadline so I couldn't work on this one right now.
I was just thinking about resetting my mental model for the Spark 2.4.x code
execution performance, and saw that after the fallback was implemented, it's
very hard for the user to figure out whether or not the interpreter fallback is
taking effect and/or whether or not it's contributing to slow performance. This
would be valuable information to have for query tuning, etc.
> Add optional logging to UnsafeProjection.create when it falls back to
> interpreted mode
> --------------------------------------------------------------------------------------
>
> Key: SPARK-25140
> URL: https://issues.apache.org/jira/browse/SPARK-25140
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.4.0
> Reporter: Kris Mok
> Priority: Minor
>
> SPARK-23711 implemented a nice graceful handling of allowing UnsafeProjection
> to fall back to an interpreter mode when codegen fails. That makes Spark much
> more usable even when codegen is unable to handle the given query.
> But in its current form, the fallback handling can also be a mystery in terms
> of performance cliffs. Users may be left wondering why a query runs fine with
> some expressions, but then with just one extra expression the performance
> goes 2x, 3x (or more) slower.
> It'd be nice to have optional logging of the fallback behavior, so that for
> users that care about monitoring performance cliffs, they can opt-in to log
> when a fallback to interpreter mode was taken. i.e. at
> https://github.com/apache/spark/blob/a40ffc656d62372da85e0fa932b67207839e7fde/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Projection.scala#L183
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