[jira] [Updated] (SPARK-54621) Merge Into Update Set * preserve nested fields if coerceNestedTypes is enabled

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-54621?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

ASF GitHub Bot updated SPARK-54621:
-----------------------------------
    Labels: pull-request-available  (was: )

> Merge Into Update Set * preserve nested fields if coerceNestedTypes is enabled
> ------------------------------------------------------------------------------
>
>                 Key: SPARK-54621
>                 URL: https://issues.apache.org/jira/browse/SPARK-54621
>             Project: Spark
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions: 4.1.0
>            Reporter: Szehon Ho
>            Priority: Major
>              Labels: pull-request-available
>
> The 'struct coercion' feature for MERGE INTO (allowing it to pass if assigning a struct with less fields into a struct with more fields) is turned off in a flag in SPARK-54525, but was not removed because the community wanted to try it.
> [~aokolnychyi] tested the feature and thinks that even if it is behind the experimental flag, we should take the stance for now that UPDATE SET * should explode to all nested fields vs top level columns.  Ie in this case, missing nested fields are preserved, and not overriden with null if we only explode it top-level columns.
> The rationale being:
> * its safer to not override values
> * Spark in general tries to treat nested fields like columns
> * there's a way for the user to override with null, in particular by specifying the struct explicitly, ie UPDATE SET struct = source.struct



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