[jira] [Commented] (SPARK-18637) Stateful UDF should be considered as nondeterministic

["Zhan Zhang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-18637?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15706905#comment-15706905 ] 

Zhan Zhang commented on SPARK-18637:
------------------------------------

Here is the comments from UDFType 
  /**
   * If a UDF stores state based on the sequence of records it has processed, it
   * is stateful. A stateful UDF cannot be used in certain expressions such as
   * case statement and certain optimizations such as AND/OR short circuiting
   * don't apply for such UDFs, as they need to be invoked for each record.
   * row_sequence is an example of stateful UDF. A stateful UDF is considered to
   * be non-deterministic, irrespective of what deterministic() returns.
   *
   * @return true
   */
  boolean stateful() default false;

> Stateful UDF should be considered as nondeterministic
> -----------------------------------------------------
>
>                 Key: SPARK-18637
>                 URL: https://issues.apache.org/jira/browse/SPARK-18637
>             Project: Spark
>          Issue Type: Bug
>            Reporter: Zhan Zhang
>
> If the annotation UDFType of a udf is stateful, it shoudl be considered as non-deterministic. Otherwise, the catalyst may optimize the plan and return the wrong result.



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