[jira] [Commented] (SPARK-30006) printSchema indeterministic output

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

    [ https://issues.apache.org/jira/browse/SPARK-30006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16981407#comment-16981407 ] 

Kun commented on SPARK-30006:
-----------------------------

In the constructor of *pyspark.sql.Row*, the fields order get sorted by the name. So the order changes.

Is the sorting by design?
{code:python}
class Row(tuple):
    def __new__(self, *args, **kwargs):
        if args and kwargs:
            raise ValueError("Can not use both args "
                             "and kwargs to create Row")
        if kwargs:
            # create row objects
            names = sorted(kwargs.keys())
            row = tuple.__new__(self, [kwargs[n] for n in names])
            row.__fields__ = names
            row.__from_dict__ = True
            return row

        else:
            # create row class or objects
            return tuple.__new__(self, args)
{code}

> printSchema indeterministic output
> ----------------------------------
>
>                 Key: SPARK-30006
>                 URL: https://issues.apache.org/jira/browse/SPARK-30006
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 2.4.4
>            Reporter: Hasil Sharma
>            Priority: Minor
>
> printSchema doesn't give a consistent output in following example.
>  
> {code:python}
> from pyspark.sql import SparkSession
> from pyspark.sql import Row
> spark = SparkSession.builder.appName("new-session").getOrCreate()
> l = [('Ankit',25),('Jalfaizy',22),('saurabh',20),('Bala',26)]
> rdd = spark.sparkContext.parallelize(l)
> people = rdd.map(lambda x: Row(name=x[0], age=int(x[1])))
> df1 = spark.createDataFrame(people)
> print(df1.printSchema())
> df2 = df1.select("name", "age")
> print(df2.printSchema())
> {code}
>  
> first print outputs
> {noformat}
> root
> |– age: long (nullable = true)
> |– name: string (nullable = true)
> {noformat}
>  
> second print outputs
> {noformat}
> root
> |– name: string (nullable = true)
> |– age: long (nullable = true)
> {noformat}
> Expectation: The output should be same because the column names are same.



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