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Date: Mon, 12 Sep 2011 22:41:08 +0000 (UTC)
From: "Carl Steinbach (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
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Subject: [jira] [Reopened] (HIVE-2327) UDFs should be made aware when their
 arguments are constants.
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     [ https://issues.apache.org/jira/browse/HIVE-2327?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Carl Steinbach reopened HIVE-2327:
----------------------------------


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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