[jira] [Commented] (SPARK-37575) null values should be saved as nothing rather than quoted empty Strings "" with default settings

["Apache Spark (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-37575?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17519235#comment-17519235 ] 

Apache Spark commented on SPARK-37575:
--------------------------------------

User 'anchovYu' has created a pull request for this issue:
https://github.com/apache/spark/pull/36110

> null values should be saved as nothing rather than quoted empty Strings "" with default settings
> ------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-37575
>                 URL: https://issues.apache.org/jira/browse/SPARK-37575
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.4.0, 3.2.0
>            Reporter: Wei Guo
>            Assignee: Wei Guo
>            Priority: Major
>             Fix For: 3.3.0
>
>
> As mentioned in sql migration guide([https://spark.apache.org/docs/latest/sql-migration-guide.html#upgrading-from-spark-sql-23-to-24]),
> {noformat}
> Since Spark 2.4, empty strings are saved as quoted empty strings "". In version 2.3 and earlier, empty strings are equal to null values and do not reflect to any characters in saved CSV files. For example, the row of "a", null, "", 1 was written as a,,,1. Since Spark 2.4, the same row is saved as a,,"",1. To restore the previous behavior, set the CSV option emptyValue to empty (not quoted) string.{noformat}
> But actually, both empty strings and null values are saved as quoted empty Strings "" rather than "" (for empty strings) and nothing(for null values)。
> code:
> {code:java}
> val data = List("spark", null, "").toDF("name")
> data.coalesce(1).write.csv("spark_csv_test")
> {code}
>  actual result:
> {noformat}
> line1: spark
> line2: ""
> line3: ""{noformat}
> expected result:
> {noformat}
> line1: spark
> line2: 
> line3: ""
> {noformat}



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