Franklyn Dsouza created SPARK-19844:
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Summary: UDF in when control function is executed before the when
clause is evaluated.
Key: SPARK-19844
URL: https://issues.apache.org/jira/browse/SPARK-19844
Project: Spark
Issue Type: Bug
Components: PySpark, SQL
Affects Versions: 2.1.0, 2.0.1
Reporter: Franklyn Dsouza
Sometimes we try to filter out the argument to a udf using {code}when(clause,
udf).otherwise(default){code}
but we've noticed that sometimes the udf is being run on data that shouldn't
have matched the clause.
heres some code to reproduce the issue.
{code}
from pyspark.sql import functions as F
from pyspark.sql import types
df = sc.sql.createDataFrame([{'r': None}],
schema=types.StructType([types.StructField('r', types.StringType())]))
simple_udf = F.udf(lambda ref: ref.strip("/"), types.StringType())
df.withColumn('test',
F.when(F.col("r").isNotNull(), simple_udf(F.col("r")))
.otherwise(F.lit(None))
).collect()
{code}
This causes an exception because the udf is running on null data. i get
AttributeError: 'NoneType' object has no attribute 'strip'.
so it looks like the udf is being evaluated before the clause in the when is
evaulated. Oddly enough when i change {code}F.col("r").isNotNull(){code} to
{code}df["r"] != None{code} then it works.
might be related to https://issues.apache.org/jira/browse/SPARK-13773
and https://issues.apache.org/jira/browse/SPARK-15282
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