[jira] [Created] (SPARK-10588) Saving a DataFrame containing only nulls to JSON doesn't work

["Cheng Lian (JIRA)" <ji...@apache.org>]

Cheng Lian created SPARK-10588:
----------------------------------

             Summary: Saving a DataFrame containing only nulls to JSON doesn't work
                 Key: SPARK-10588
                 URL: https://issues.apache.org/jira/browse/SPARK-10588
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 1.5.0
            Reporter: Cheng Lian


Snippets to reproduce this issue:
{noformat}
val path = "file:///tmp/spark/null"

// A single row containing a single null double, saving to JSON, wrong
sqlContext.
  range(1).selectExpr("CAST(NULL AS DOUBLE) AS c0").
  write.mode("overwrite").json(path)

sqlContext.read.json(path).show()

++
||
++
||
++

// Two rows each containing a single null double, saving to JSON, wrong
sqlContext.
  range(2).selectExpr("CAST(NULL AS DOUBLE) AS c0").
  write.mode("overwrite").json(path)

sqlContext.read.json(path).show()

++
||
++
||
||
++

// A single row containing two null doubles, saving to JSON, wrong
sqlContext.
  range(1).selectExpr("CAST(NULL AS DOUBLE) AS c0", "CAST(NULL AS DOUBLE) AS c1").
  write.mode("overwrite").json(path)

sqlContext.read.json(path).show()

++
||
++
||
++

// A single row containing a single null double, saving to Parquet, OK
sqlContext.
  range(1).selectExpr("CAST(NULL AS DOUBLE) AS c0").
  write.mode("overwrite").parquet(path)

sqlContext.read.parquet(path).show()

+----+
|   d|
+----+
|null|
+----+

// Two rows, one containing a single null double, one containing non-null double, saving to JSON, OK
sqlContext.
  range(2).selectExpr("IF(id % 2 = 0, CAST(NULL AS DOUBLE), id) AS c0").
  write.mode("overwrite").json(path)

sqlContext.read.json(path).show()

+----+
|   d|
+----+
|null|
| 1.0|
+----+
{noformat}



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