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https://issues.apache.org/jira/browse/HIVE-4014?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13586701#comment-13586701
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Lianhui Wang commented on HIVE-4014:
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i donot think that.
i see the code.
in HiveInputFormat and CombineHiveInputFormat's getRecordReader()， it calls
pushProjectionsAndFilters().
also in pushProjectionsAndFilters(), from TableScanOperator it get needed
columns and set these ids to hive.io.file.readcolumn.ids.
and then in RCFile.Reader will read hive.io.file.readcolumn.ids to skip column.
maybe the counter has some mistakes.
if i have mistake,please tell me.thx.
> Hive+RCFile is not doing column pruning and reading much more data than
> necessary
> ---------------------------------------------------------------------------------
>
> Key: HIVE-4014
> URL: https://issues.apache.org/jira/browse/HIVE-4014
> Project: Hive
> Issue Type: Bug
> Reporter: Vinod Kumar Vavilapalli
> Assignee: Vinod Kumar Vavilapalli
>
> With even simple projection queries, I see that HDFS bytes read counter
> doesn't show any reduction in the amount of data read.
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