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https://issues.apache.org/jira/browse/SPARK-17480?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15478035#comment-15478035
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Sean Owen commented on SPARK-17480:
-----------------------------------
Yeah, I wonder if the "unrolled" while loop here is really the right way to do
it. You can certainly solve the problem by just computing the length once, but,
I don't really see why
{{compressionEncoders.foreach(_.gatherCompressibilityStats(row, ordinal))}}
isn't just simpler and probably no different performance-wise.
> CompressibleColumnBuilder inefficiently call gatherCompressibilityStats
> ------------------------------------------------------------------------
>
> Key: SPARK-17480
> URL: https://issues.apache.org/jira/browse/SPARK-17480
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Reporter: Ergin Seyfe
> Priority: Minor
>
> When we profile one of our Spark jobs we saw that:
> 6.24% of the CPU is spend on List.length.
> Scala List's length method is O(N) =>
> https://github.com/scala/scala/blob/2.10.x/src/library/scala/collection/LinearSeqOptimized.scala#L36
> Since we loop this method becomes O(N^2)
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