Juliusz Sompolski created SPARK-20367:
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             Summary: Spark silently escapes partition column names
                 Key: SPARK-20367
                 URL: https://issues.apache.org/jira/browse/SPARK-20367
             Project: Spark
          Issue Type: Bug
          Components: Spark Core
    Affects Versions: 2.1.0, 2.2.0
            Reporter: Juliusz Sompolski
            Priority: Minor


CSV files can have arbitrary column names:
{code}
scala> spark.range(1).select(col("id").as("Column?"), 
col("id")).write.option("header", true).csv("/tmp/foo")
scala> spark.read.option("header", true).csv("/tmp/foo").schema
res1: org.apache.spark.sql.types.StructType = 
StructType(StructField(Column?,StringType,true), 
StructField(id,StringType,true))
{code}
However, once a column with characters like "?" in the name gets used in a 
partitioning column, the column name gets silently escaped, and reading the 
schema information back renders the column name with "?" turned into "%3F":
{code}
scala> spark.range(1).select(col("id").as("Column?"), 
col("id")).write.partitionBy("Column?").option("header", true).csv("/tmp/bar")
scala> spark.read.option("header", true).csv("/tmp/bar").schema
res3: org.apache.spark.sql.types.StructType = 
StructType(StructField(id,StringType,true), 
StructField(Column%3F,IntegerType,true))
{code}
The same happens for other formats, but I encountered it working with CSV, 
since these more often contain ugly schemas... 

Not sure if it's a bug or a feature, but it might be more intuitive to fail 
queries with invalid characters in the partitioning column name, rather than 
silently escaping the name?



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