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https://issues.apache.org/jira/browse/SPARK-25829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16663118#comment-16663118
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Wenchen Fan commented on SPARK-25829:
-------------------------------------
More investigation on "later entry wins".
If we still allow duplicated keys in map physically, following functions need
to be updated:
Explode, PosExplode, GetMapValue, MapKeys, MapValues, MapEntries,
TransformKeys, TransformValues, MapZipWith
If we want to forbid duplicated keys in map, following functions need to be
updated:
CreateMap, MapFromArrays, MapFromEntries, MapConcat, MapFilter, and also
reading map from data sources.
So "later entry wins" semantic is more ideal but needs more works.
> Duplicated map keys are not handled consistently
> ------------------------------------------------
>
> Key: SPARK-25829
> URL: https://issues.apache.org/jira/browse/SPARK-25829
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.4.0
> Reporter: Wenchen Fan
> Priority: Major
>
> In Spark SQL, we apply "earlier entry wins" semantic to duplicated map keys.
> e.g.
> {code}
> scala> sql("SELECT map(1,2,1,3)[1]").show
> +------------------+
> |map(1, 2, 1, 3)[1]|
> +------------------+
> | 2|
> +------------------+
> {code}
> However, this handling is not applied consistently.
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