Hyukjin Kwon created SPARK-15473:
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             Summary: CSV fails to write empty dataframe
                 Key: SPARK-15473
                 URL: https://issues.apache.org/jira/browse/SPARK-15473
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 2.0.0
            Reporter: Hyukjin Kwon


Currently CSV data source fails to write and read empty data.

The code below:

{code}
val emptyDf = spark.range(10).filter(_ => false)
emptyDf.write
  .format("csv")
  .save(path.getCanonicalPath)

val copyEmptyDf = spark.read
  .format("csv")
  .load(path.getCanonicalPath)

copyEmptyDf.show()
{code}

throws an exception below:

{code}

Can not create a Path from an empty string
java.lang.IllegalArgumentException: Can not create a Path from an empty string
        at org.apache.hadoop.fs.Path.checkPathArg(Path.java:127)
        at org.apache.hadoop.fs.Path.<init>(Path.java:135)
        at org.apache.hadoop.util.StringUtils.stringToPath(StringUtils.java:241)
        at 
org.apache.hadoop.mapred.FileInputFormat.setInputPaths(FileInputFormat.java:362)
        at 
org.apache.spark.SparkContext$$anonfun$hadoopFile$1$$anonfun$32.apply(SparkContext.scala:987)
        at 
org.apache.spark.SparkContext$$anonfun$hadoopFile$1$$anonfun$32.apply(SparkContext.scala:987)
        at 
org.apache.spark.rdd.HadoopRDD$$anonfun$getJobConf$6.apply(HadoopRDD.scala:178)
        at 
org.apache.spark.rdd.HadoopRDD$$anonfun$getJobConf$6.apply(HadoopRDD.scala:178)
        at scala.Option.map(Option.scala:146)
{code}


Note that this is a different case with the data below

{code}
val emptyDf = spark.createDataFrame(spark.sparkContext.emptyRDD[Row], schema)
{code}

In this case, any writer is not initialised and created. (no calls of 
{{WriterContainer.writeRows()}}.

Maybe, it should be able to read/write header for schemas as well as empty data.



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