Ala Luszczak created SPARK-26147:
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Summary: Python UDFs in join condition fail even when using
columns from only one side of join
Key: SPARK-26147
URL: https://issues.apache.org/jira/browse/SPARK-26147
Project: Spark
Issue Type: Bug
Components: PySpark
Affects Versions: 2.4.0
Reporter: Ala Luszczak
The rule {{PullOutPythonUDFInJoinCondition}} was implemented in
[https://github.com/apache/spark/commit/2a8cbfddba2a59d144b32910c68c22d0199093fe]
As far as I understand, this rule was intended to prevent the use of Python
UDFs in join condition if they take arguments from both sides of the join, and
this doesn't make sense in combination with the join type.
The rule {{PullOutPythonUDFInJoinCondition}} seems to make an assumption, that
if a given UDF is only using columns from a single side of the join, it will be
already pushed down under the join before this rule is executed.
However, this is not always the case. Here's a simple example that fails, even
though it looks like it should run just fine (and it does in earlier versions
of Spark):
{code:java}
from pyspark.sql import Row
from pyspark.sql.types import StringType
from pyspark.sql.functions import udf
cars_list = [ Row("NL", "1234AB"), Row("UK", "987654") ]
insurance_list = [ Row("NL-1234AB"), Row("BE-112233") ]
spark.createDataFrame(data = cars_list, schema = ["country",
"plate_nr"]).createOrReplaceTempView("cars")
spark.createDataFrame(data = insurance_list, schema =
["insurance_code"]).createOrReplaceTempView("insurance")
to_insurance_code = udf(lambda x, y: x + "-" + y, StringType())
sqlContext.udf.register('to_insurance_code', to_insurance_code)
spark.conf.set("spark.sql.crossJoin.enabled", "true")
# This query runs just fine.
sql("""
SELECT country, plate_nr, insurance_code
FROM cars LEFT OUTER JOIN insurance
ON CONCAT(country, '-', plate_nr) = insurance_code
""").show()
# This equivalent query fails with:
# pyspark.sql.utils.AnalysisException: u'Using PythonUDF in join condition of
join type LeftOuter is not supported.;'
sql("""
SELECT country, plate_nr, insurance_code
FROM cars LEFT OUTER JOIN insurance
ON to_insurance_code(country, plate_nr) = insurance_code
""").show()
{code}
[~cloud_fan] [~XuanYuan] fyi
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