GitHub user maropu opened a pull request:
https://github.com/apache/spark/pull/17347
[SPARK-19980][SQL] Add NULL checks in Bean serializer
## What changes were proposed in this pull request?
A Bean serializer in `ExpressionEncoder` could change values when Beans
having NULL. A concrete example is as follows;
```
scala> :paste
class Outer extends Serializable {
private var cls: Inner = _
def setCls(c: Inner): Unit = cls = c
def getCls(): Inner = cls
}
class Inner extends Serializable {
private var str: String = _
def setStr(s: String): Unit = str = str
def getStr(): String = str
}
scala> Seq("""{"cls":null}""", """{"cls":
{"str":null}}""").toDF().write.text("data")
scala> val encoder = Encoders.bean(classOf[Outer])
scala> val schema = encoder.schema
scala> val df = spark.read.schema(schema).json("data").as[Outer](encoder)
scala> df.show
+------+
| cls|
+------+
|[null]|
| null|
+------+
scala> df.map(x => x)(encoder).show()
+------+
| cls|
+------+
|[null]|
|[null]| // <-- Value changed
+------+
```
This is because the Bean serializer does not have the NULL-check
expressions that the serializer of Scala's product types has. Actually, this
value change does not happen in Scala's product types;
```
scala> :paste
case class Outer(cls: Inner)
case class Inner(str: String)
scala> val encoder = Encoders.product[Outer]
scala> val schema = encoder.schema
scala> val df = spark.read.schema(schema).json("data").as[Outer](encoder)
scala> df.show
+------+
| cls|
+------+
|[null]|
| null|
+------+
scala> df.map(x => x)(encoder).show()
+------+
| cls|
+------+
|[null]|
| null|
+------+
```
This pr added the NULL-check expressions in Bean serializer along with the
serializer of Scala's product types.
## How was this patch tested?
Added tests in `JavaDatasetSuite`.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/maropu/spark SPARK-19980
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/17347.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #17347
----
commit 093b4e3baecf8a92b9e1218ae1b39b76120a826b
Author: Takeshi Yamamuro <yamam...@apache.org>
Date: 2017-03-19T11:03:01Z
Add null checks in Bean serializer
----
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