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https://issues.apache.org/jira/browse/HIVE-2327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14543059#comment-14543059
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Alexander Pivovarov commented on HIVE-2327:
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I run vectorization_short_regress.q test locally and noticed couple changes in
q.out file
- rlike is replaced with regexp (they are synonyms)
- parentesises around "(a regexp b)" are removed in explain query output.
I also noticed that old UDFRegExp registration set isOperator=true
{code}
system.registerUDF("rlike", UDFRegExp.class, true);
system.registerUDF("regexp", UDFRegExp.class, true);
{code}
But new implementation extends GenericUDF. Generic UDF registration does not
have isOperator parameter. Can it cause any issues?
{code}
system.registerGenericUDF("rlike", GenericUDFRegExp.class);
system.registerGenericUDF("regexp", GenericUDFRegExp.class);
{code}
> Optimize REGEX UDFs with constant parameter information
> -------------------------------------------------------
>
> Key: HIVE-2327
> URL: https://issues.apache.org/jira/browse/HIVE-2327
> Project: Hive
> Issue Type: Improvement
> Components: UDF
> Reporter: Adam Kramer
> Assignee: Alexander Pivovarov
> Attachments: HIVE-2327.01.patch
>
>
> 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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