[jira] [Commented] (SPARK-23693) SQL function uuid()

["Jean Georges Perrin (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-23693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17400411#comment-17400411 ] 

Jean Georges Perrin commented on SPARK-23693:
---------------------------------------------

[~rxin] - You could require a parameter to the function this should make it deterministic.

> SQL function uuid()
> -------------------
>
>                 Key: SPARK-23693
>                 URL: https://issues.apache.org/jira/browse/SPARK-23693
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 2.2.1, 2.3.0
>            Reporter: Arseniy Tashoyan
>            Priority: Minor
>
> Add function uuid() to org.apache.spark.sql.functions that returns [Universally Unique ID|https://en.wikipedia.org/wiki/Universally_unique_identifier].
> Sometimes it is necessary to uniquely identify each row in a DataFrame.
> Currently the following ways are available:
>  * monotonically_increasing_id() function
>  * row_number() function over some window
>  * convert the DataFrame to RDD and zipWithIndex()
> All these approaches do not work when appending this DataFrame to another DataFrame (union). Collisions may occur - two rows in different DataFrames may have the same ID. Re-generating IDs on the resulting DataFrame is not an option, because some data in some other system may already refer to old IDs.
> The proposed solution is to add new function:
> {code:scala}
> def uuid(): Column
> {code}
> that returns String representation of UUID.
> UUID is represented as a 128-bit number (two long numbers). Such numbers are not supported in Scala or Java. In addition, some storage systems do not support 128-bit numbers (Parquet's largest numeric type is INT96). This is the reason for the uuid() function to return String.
> I already have a simple implementation based on [java-uuid-generator|https://github.com/cowtowncoder/java-uuid-generator]. I can share it as a PR.



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