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https://issues.apache.org/jira/browse/HIVE-2327?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Carl Steinbach reopened HIVE-2327:
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HIVE-1360 made it possible for UDFs to detect constant parameters, but it
didn't update any of the regex UDFs to take advantage of this feature.
> UDFs should be made aware when their arguments are constants.
> -------------------------------------------------------------
>
> Key: HIVE-2327
> URL: https://issues.apache.org/jira/browse/HIVE-2327
> Project: Hive
> Issue Type: Improvement
> Reporter: Adam Kramer
>
> There are a lot of UDFs which would show major performance differences if one
> assumes that some of its arguments are constant.
> Consider, for example, any UDF that takes a regular expression as input: This
> can be complied once (fast) if it's a constant, or once per row (wicked slow)
> if it's not a constant.
> Or, consider any UDF that reads from a file and/or takes a filename as input;
> it would have to re-read the whole file if the filename changes.
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