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https://issues.apache.org/jira/browse/SPARK-18736?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15726074#comment-15726074
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Shuai Lin commented on SPARK-18736:
-----------------------------------
If the keys are all literas, then we can detect and remove the duplicated keys
during analysis.
But if there are non-literal keys, we can't detect this before the physical
execution, e.g.:
{code}
spark.createDataFrame(
Seq(
(1, "aaa"),
(2, "bbb"),
(3, "ccc")
)).toDF("id", "name").registerTempTable("df")
sql("select map(name, id, 'aaa', -1) as m from df").show()
{code}
So I think we can do this in two places:
* When preparing the {{keys}} and {{values}} expressions, we can remove all
duplicated literal keys.
* When doing codegen, we can add logic to discard the duplicated keys if there
is any (e.g. by tracking the keys in a set)
[~hvanhovell] Does it sound good?
> CreateMap allows non-unique keys
> --------------------------------
>
> Key: SPARK-18736
> URL: https://issues.apache.org/jira/browse/SPARK-18736
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.0.0
> Reporter: Eyal Farago
> Labels: map, sql, types
>
> Spark-Sql, {{CreateMap}} does not enforce unique keys, i.e. it's possible to
> create a map with two identical keys:
> {noformat}
> CreateMap(Literal(1), Literal(11), Literal(1), Literal(12))
> {noformat}
> This does not behave like standard maps in common programming languages.
> proper behavior should be chosen:
> # first 'wins'
> # last 'wins'
> # runtime error.
> {{GetMapValue}} currently implements option #1. Even if this is the desired
> behavior {{CreateMap}} should return a unique map.
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