Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/16976#discussion_r120034550
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/DataFrameReader.scala ---
@@ -463,6 +463,7 @@ class DataFrameReader private[sql](sparkSession:
SparkSession) extends Logging {
* <li>`columnNameOfCorruptRecord` (default is the value specified in
* `spark.sql.columnNameOfCorruptRecord`): allows renaming the new field
having malformed string
* created by `PERMISSIVE` mode. This overrides
`spark.sql.columnNameOfCorruptRecord`.</li>
+ * <li>`wholeFile` (default `false`): parse one record, which may span
multiple lines.</li>
--- End diff --
Definitely. I wanted to emphasize multiple lines is not _per file_.
For example, CSV reads multiple records (multiple lines) per file (newline
is replaced to `\n` manually for readability).
```csv
"I am
Hyukjin Kwon"
"Hyukjin Kwon
I love Spark!"
```
```scala
scala> spark.read.option("wholeFile", true).csv("test.csv").show()
+---------------------+
| _c0|
+---------------------+
| I am\nHyukjin Kwon|
|Hyukjin Kwon\nI lo...|
+---------------------+
```
Whereas JSON reads the record _per file_. I am pretty sure object root
support is primary.
```json
{
"I am": "HyukjinKwon",
"HyukjinKwon": "I love Spark!"
}
```
```scala
scala> spark.read.option("wholeFile", true).json("test.json").show()
+-------------+-----------+
| HyukjinKwon| I am|
+-------------+-----------+
|I love Spark!|HyukjinKwon|
+-------------+-----------+
```
but note that it could (in terms of input/output), work similarly with CSV
when the input is a json array.
```json
[{
"I am": "HyukjinKwon",
"HyukjinKwon": "I love Spark!"
},{
"I am": "HyukjinKwon",
"HyukjinKwon": "I love Spark!"
}]
```
```scala
scala> spark.read.option("wholeFile", true).json("test.json").show()
+-------------+-----------+
| HyukjinKwon| I am|
+-------------+-----------+
|I love Spark!|HyukjinKwon|
|I love Spark!|HyukjinKwon|
+-------------+-----------+
```
Comparing array case and CSV, they work still differently. JSON, up to my
knowledge, parses whole files and produces each record (in case or an array)
whereas CSV parses record by record from the stream.
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