Josh Rosen created SPARK-2737: --------------------------------- Summary: ClassCastExceptions when collect()ing JavaRDDs' underlying Scala RDDs Key: SPARK-2737 URL: https://issues.apache.org/jira/browse/SPARK-2737 Project: Spark Issue Type: Bug Components: Java API Affects Versions: 1.0.0, 0.9.0, 0.8.0 Reporter: Josh Rosen Assignee: Josh Rosen
The Java API's use of fake ClassTags doesn't seem to cause any problems for Java users, but it can lead to issues when passing JavaRDDs' underlying RDDs to Scala code (e.g. in the MLlib Java API wrapper code). If we call {{collect()}} on a Scala RDD with an incorrect ClassTag, this causes ClassCastExceptions when we try to allocate an array of the wrong type (for example, see SPARK-2197). There are a few possible fixes here. An API-breaking fix would be to completely remove the fake ClassTags and require Java API users to pass {{java.lang.Class}} instances to all {{parallelize()}} calls and add {{returnClass}} fields to all {{Function}} implementations. This would be extremely verbose. Instead, I propose that we add internal APIs to "repair" a Scala RDD with an incorrect ClassTag by wrapping it and overriding its ClassTag. This should be okay for cases where the Scala code that calls {{collect()}} knows what type of array should be allocated, which is the case in the MLlib wrappers. -- This message was sent by Atlassian JIRA (v6.2#6252)