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https://issues.apache.org/jira/browse/SPARK-48530?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wenchen Fan reassigned SPARK-48530:
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Assignee: David Milicevic
> [M1] Support for local variables
> --------------------------------
>
> Key: SPARK-48530
> URL: https://issues.apache.org/jira/browse/SPARK-48530
> Project: Spark
> Issue Type: Sub-task
> Components: Spark Core
> Affects Versions: 4.0.0
> Reporter: David Milicevic
> Assignee: David Milicevic
> Priority: Major
> Labels: pull-request-available
>
> At the moment, variables in SQL scripts are creating session variables. We
> don't want this, we want variables to be considered as local (within the
> block/compound).
>
> -To achieve this, we probably need to wait for labels support. Once we have
> it, we can prepend variable names with labels to make distinction between
> variables with the same name and only then reuse session variables mechanism
> to save values with such composed names.-
> -If the block/compound doesn't have label, we should generate it
> automatically (GUID or something similar).-
>
> Labels support is done, so we can use them now for local variables - they
> need to be able to be referenced by <labelName>.<varName>.
> We cannot reuse session variables for this - we need to implement local
> variables per script, with scoping and shadowing.
>
> Session variables need to be able to be accessed by
> `system.session.<varName>` at all times from the script though.
>
> -Also, variables cannot recover from script failures - if a script fails,
> variables won’t be dropped. If we intend to reuse session variables for local
> variables, we should think about how to fix this.- We won't be using session
> variables, so this shouldn't be a problem, but need to have it in mind
> because wrong implementation can cause the same problem.
>
> Use [Session Variables PR|https://github.com/apache/spark/pull/40474/files]
> as a reference in which places variable changes need to happen.
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