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https://issues.apache.org/jira/browse/SPARK-18457?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Reynold Xin resolved SPARK-18457.
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Resolution: Fixed
Assignee: Andrew Ray
Fix Version/s: 2.1.0
> ORC and other columnar formats using HiveShim read all columns when doing a
> simple count
> ----------------------------------------------------------------------------------------
>
> Key: SPARK-18457
> URL: https://issues.apache.org/jira/browse/SPARK-18457
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 1.6.3, 2.0.2
> Environment: Hadoop 2.7.0
> Reporter: Andrew Ray
> Assignee: Andrew Ray
> Priority: Minor
> Fix For: 2.1.0
>
>
> Doing a `select count(*) from a_orc_table` reads all columns and thus is
> slower than a query selecting one like `select count(a_column) from
> a_orc_table`. Data read can be seen in the UI (appears to only be accurate
> for Hadoop 2.5+ based on comment in FileScanRDD.scala line 80).
> I will create a PR shortly.
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