[jira] [Created] (SPARK-22629) handling of random in UDFs

["Michael H (JIRA)" <ji...@apache.org>]

Michael H created SPARK-22629:
---------------------------------

             Summary: handling of random in UDFs
                 Key: SPARK-22629
                 URL: https://issues.apache.org/jira/browse/SPARK-22629
             Project: Spark
          Issue Type: Bug
          Components: PySpark
    Affects Versions: 2.1.0
            Reporter: Michael H


df_br = spark.createDataFrame([{'name': 'hello'}])

# create a random int
udf_random_col =  udf(lambda: int(100*random.random()), IntegerType())

# add ten
random.seed(1234)
udf_add_ten =  udf(lambda rand: rand + 10, IntegerType())

# add a column with a random value to that DF
df_br = df_br.withColumn('RAND', udf_random_col())
df_br.show()

+-----+----+
| name|RAND|
+-----+----+
|hello|  68|
+-----+----+

# unexpected result due to re-evaluation
df_br.withColumn('RAND_PLUS_TEN', udf_add_ten('RAND')).show()

+-----+----+-------------+
| name|RAND|RAND_PLUS_TEN|
+-----+----+-------------+
|hello|  72|           87|
+-----+----+-------------+

# workaround: cache the resulst after using the random number generating udf
df_br.withColumn('RAND', udf_random_col()).cache().withColumn('RAND_PLUS_TEN', udf_add_ten('RAND')).show()

+-----+----+-------------+
| name|RAND|RAND_PLUS_TEN|
+-----+----+-------------+
|hello|  68|           78|
+-----+----+-------------+




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