[SPARK-16998] select($"column1", explode($"column2")) is extremely slow

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.2.0
• Component/s: SQL
• Assignee: Herman van Hövell
• Reporter: TobiasP
• Created: 10/Aug/16 16:25
• Updated: 19/Nov/17 05:47
• Resolved: 20/Nov/16 16:07

Description

Using a Dataset containing 10.000 rows, each containing null and an array of 5.000 Ints, I observe the following performance (in local mode):

scala> time(ds.select(explode($"value")).sample(false, 0.0000001, 1).collect)
1.219052 seconds                                                                
res9: Array[org.apache.spark.sql.Row] = Array([3761], [3766], [3196])

scala> time(ds.select($"dummy", explode($"value")).sample(false, 0.0000001, 1).collect)
20.219447 seconds                                                               
res5: Array[org.apache.spark.sql.Row] = Array([null,3761], [null,3766], [null,3196])

Issue Links

• duplicates: SPARK-15214 Implement code generation for Generate
• is related to: SPARK-21657 Spark has exponential time complexity to explode(array of structs)