[SPARK-4812] SparkPlan.codegenEnabled may be initialized to a wrong value

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.3.0
• Component/s: SQL
• Target Version/s: 1.3.0
• Assignee: Shixiong Zhu
• Reporter: Shixiong Zhu
• Created: 10/Dec/14 07:26
• Updated: 16/Dec/14 22:38
• Resolved: 16/Dec/14 22:38

Description

The problem is `codegenEnabled` is `val`, but it uses a `val` `sqlContext`, which can be override by subclasses. Here is a simple example to show this issue.

scala> :paste
// Entering paste mode (ctrl-D to finish)

abstract class Foo {

  protected val sqlContext = "Foo"

  val codegenEnabled: Boolean = {
    println(sqlContext) // it will call subclass's `sqlContext` which has not yet been initialized.
    if (sqlContext != null) {
      true
    } else {
      false
    }
  }
}

class Bar extends Foo {
  override val sqlContext = "Bar"
}

println(new Bar().codegenEnabled)

// Exiting paste mode, now interpreting.

null
false
defined class Foo
defined class Bar

scala> 

We should make `sqlContext` `final` to prevent subclasses from overriding it incorrectly.

Issue Links

• links to: [Github] Pull Request #3660 (zsxwing)