[jira] [Created] (SPARK-45745) Extremely slow execution of sum of columns in Spark 3.4.1

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

Javier created SPARK-45745:
------------------------------

             Summary: Extremely slow execution of sum of columns in Spark 3.4.1
                 Key: SPARK-45745
                 URL: https://issues.apache.org/jira/browse/SPARK-45745
             Project: Spark
          Issue Type: Bug
          Components: PySpark
    Affects Versions: 3.4.1
            Reporter: Javier


We are in the process of upgrading some pySpark jobs from Spark 3.1.2 to Spark 3.4.1 and some code that was running fine is now basically never ending even for small dataframes.

We have simplified the problematic piece of code and the minimum pySpark example below shows the issue:
{code:java}
n_cols = 50
data = [{f"col{i}": i for i in range(n_cols)} for _ in range(5)]
df_data = sql_context.createDataFrame(data)

df_data = df_data.withColumn(
    "col_sum", sum([F.col(f"col{i}") for i in range(n_cols)])
)
df_data.show(10, False) {code}
Basically, this code with Spark 3.1.2 runs fine but with 3.4.1 the computation time seems to explode when the value of `n_cols` is bigger than about 25 columns. A colleague suggested that it could be related to the limit of 22 elements in a tuple in Scala 2.13, since the 25 columns are suspiciously close to this. Is there any known defect in the logical plan optimization in 3.4.1? Or is this kind of operations (sum of multiple columns) supposed to be implemented differently?



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