[SPARK-11011][SQL] Narrow type of UDT serialization

[jodersky]

What changes were proposed in this pull request?

Narrow down the parameter type of UserDefinedType#serialize(). Currently, the parameter type is Any, however it would logically make more sense to narrow it down to the type of the actual user defined type.

How was this patch tested?

Existing tests were successfully run on local machine.

[jodersky]

It might also be a good idea to update the documentation. In this case, what exactly is a SQL datum?

[SparkQA]

Test build #52006 has finished for PR 11379 at commit 8f49d91.

• This patch fails MiMa tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • abstract class UserDefinedType[UserType >: Null] extends DataType with Serializable

[SparkQA]

Test build #52010 has finished for PR 11379 at commit 8164823.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[jodersky]

Latest commit only fixes a conflict in MiMa exclusion rules. Retesting should not be needed.

[SparkQA]

Test build #52579 has finished for PR 11379 at commit 61779ea.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[jodersky]

Whoops! Thanks for reminding me about the usefulness of testing, jenkins :)

[frreiss]

LGTM. Strange how cleaner Scala can fail the Scala style tests ;)

[jodersky]

It was actually a missing comma in an sbt file (MimaExcludes.scala in project/). Arguably a syntax error can be considered bad style ;)

[SparkQA]

Test build #52584 has finished for PR 11379 at commit e5fb44e.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[jodersky]

Seems unrelated and works locally. Jenkins, retest this please.

[SparkQA]

Test build #52600 has finished for PR 11379 at commit e5fb44e.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[mengxr]

+1. There was a bug in SQL internal type conversions, which might call serialize twice. This is why Any was used. The bug was fixed but I forgot to change the type back.

@yhuai Could you make a final pass?

[yhuai]

LGTM

[mengxr]

Merged into master. Thanks!