[SPARK-25426][SQL] Remove the duplicate fallback logic in UnsafeProjection

[maropu]

What changes were proposed in this pull request?

This pr removed the duplicate fallback logic in UnsafeProjection.

This pr comes from #22355.

How was this patch tested?

Added tests in CodeGeneratorWithInterpretedFallbackSuite.

[SparkQA]

Test build #96058 has finished for PR 22417 at commit 35e7911.

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

[viirya]

If we are going to get config directly from SQLConf, why do we need to pass it as a parameter here?

Can we keep this API untouched and let createCodeGeneratedObject implementation to take care of it?

Like:

object UnsafeProjection
    extends CodeGeneratorWithInterpretedFallback[Seq[Expression], UnsafeProjection] {

  override protected def createCodeGeneratedObject(in: Seq[Expression]): UnsafeProjection = {
    GenerateUnsafeProjection.generate(in, SQLConf.get.subexpressionEliminationEnabled)
  }

  ...
}

I think it is much simpler.

[maropu]

ah, yes. Looks reasonable. I'll update soon.

[SparkQA]

Test build #96073 has finished for PR 22417 at commit ea7e473.

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

[SparkQA]

Test build #96074 has finished for PR 22417 at commit e59902a.

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

[hvanhovell]

LGTM

[viirya]

LGTM too.

[maropu]

cc: @cloud-fan

[gatorsmile]

LGTM

Thanks! Merged to master.