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https://issues.apache.org/jira/browse/SPARK-27692?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16838803#comment-16838803
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Sunitha Kambhampati commented on SPARK-27692:
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I'll open a PR soon.
> Optimize evaluation of udf that is deterministic and has literal inputs
> -----------------------------------------------------------------------
>
> Key: SPARK-27692
> URL: https://issues.apache.org/jira/browse/SPARK-27692
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Sunitha Kambhampati
> Priority: Major
>
> Deterministic UDF is a udf for which the following is true: Given a specific
> input, the output of the udf will be the same no matter how many times you
> execute the udf.
> When your inputs to the UDF are all literal and UDF is deterministic, we can
> optimize this to evaluate the udf once and use the output instead of
> evaluating the UDF each time for every row in the query.
> This is valid only if the UDF is deterministic and inputs are literal.
> Otherwise we should not and cannot apply this optimization.
> *Testing:*
> We have used this internally and have seen significant performance
> improvements for some very expensive UDFs ( as expected).
> In the PR, I have added unit tests.
> *Credits:*
> Thanks to Guy Khazma([https://github.com/guykhazma]) from the IBM Haifa
> Research Team for the idea and the original implementation.
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