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Posted to issues@spark.apache.org by "Wenchen Fan (JIRA)" <ji...@apache.org> on 2018/11/15 07:29:00 UTC

[jira] [Comment Edited] (SPARK-25829) Duplicated map keys are not handled consistently

    [ https://issues.apache.org/jira/browse/SPARK-25829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16663118#comment-16663118 ] 

Wenchen Fan edited comment on SPARK-25829 at 11/15/18 7:28 AM:
---------------------------------------------------------------

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, MapFromString, MapConcat, MapFilter, and also reading map from data sources.

So "later entry wins" semantic is more ideal but needs more works.


was (Author: cloud_fan):
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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