[jira] [Commented] (SPARK-4654) Clean up DAGScheduler's getMissingParentStages() and stageDependsOn() methods

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-4654?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14228919#comment-14228919 ] 

Apache Spark commented on SPARK-4654:
-------------------------------------

User 'JoshRosen' has created a pull request for this issue:
https://github.com/apache/spark/pull/3515

> Clean up DAGScheduler's getMissingParentStages() and stageDependsOn() methods
> -----------------------------------------------------------------------------
>
>                 Key: SPARK-4654
>                 URL: https://issues.apache.org/jira/browse/SPARK-4654
>             Project: Spark
>          Issue Type: Sub-task
>          Components: Spark Core
>            Reporter: Josh Rosen
>            Assignee: Josh Rosen
>
> DAGScheduler has {{getMissingParentStages()}} and {{stageDependsOn()}} methods, which are suspiciously similar to {{getParentStages()}}.  All of these methods perform traversal of the RDD / Stage graph to inspect parent stages.  We can remove both of these methods, though: the set of parent stages is known when a {{Stage}} instance is constructed and is already stored in {{Stage.parents}}, so we can just check for missing stages by looking for unavailable stages in {{Stage.parents}}.  Similarly, we can determine whether one stage depends on another by searching {{Stage.parents}} rather than performing the entire graph traversal from scratch.



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