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https://issues.apache.org/jira/browse/SPARK-51208?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dongjoon Hyun updated SPARK-51208:
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Parent: SPARK-44111
Issue Type: Sub-task (was: Bug)
> ColumnDefinition.toV1Column should preserve EXISTS_DEFAULT resolution
> ---------------------------------------------------------------------
>
> Key: SPARK-51208
> URL: https://issues.apache.org/jira/browse/SPARK-51208
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 4.0.0
> Reporter: Szehon Ho
> Priority: Major
> Labels: pull-request-available
>
> Some external catalogs use toV1Column and fromV1Column. However, we noticed
> that toV1Column will un-resolve some already-resolved EXISTS default values.
> Long Description: When user creates a column with default value, Spark will
> resolve the user-provided CURRENT_DEFAULT sql, to make an EXISTS_DEFAULT
> value. That is done to save the values at that time, for example to resolve
> current_database(), current_user() functions. Existing data will get those
> values.
> The typical workflow is:
> {code:java}
> val existsSQL = ResolveDefaultColumns.analyze(col, type, defaultSQL)
> // save both existsSQL and defaultSQL to column metadata{code}
>
> But this code problmatically existsDefault metadata is set back to the
> original defaultSQL.
> Consuming code will get corrupted un-resolved expressions in EXISTS_DEFAULT,
> like current_user(). This means that later when these columns are read,
> these may need to be resolved again, potentially leading to data that changes
> value.
>
> While Spark code base currently does not have such catalogs, there are some
> extneral catalogs out there that are hitting this issue.
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