[SPARK-22951] count() after dropDuplicates() on emptyDataFrame returns incorrect value

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.6.2, 2.1.3, 2.2.0, 2.3.0
• Fix Version/s: 2.2.3, 2.3.0
• Component/s: SQL
• Labels: correctness
• Target Version/s: 2.2.3, 2.3.0
• Assignee: Feng Liu
• Reporter: Michael Dreibelbis
• Created: 04/Jan/18 02:13
• Updated: 02/Mar/20 07:19
• Resolved: 10/Jan/18 22:25

Description

here is a minimal Spark Application to reproduce:

import org.apache.spark.sql.SQLContext
import org.apache.spark.{SparkConf, SparkContext}


object DropDupesApp extends App {
  
  override def main(args: Array[String]): Unit = {
    val conf = new SparkConf()
      .setAppName("test")
      .setMaster("local")
    val sc = new SparkContext(conf)
    val sql = SQLContext.getOrCreate(sc)
    assert(sql.emptyDataFrame.count == 0) // expected
    assert(sql.emptyDataFrame.dropDuplicates.count == 1) // unexpected
  }
  
}

Issue Links

• links to: [Github] Pull Request #20174 (liufengdb)
• links to: GitHub Pull Request #23434