[SPARK-32291] COALESCE should not reduce the child parallelism if it is Join

• Type: Improvement
• Status: In Progress
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.1.0
• Component/s: SQL
• Assignee: Unassigned
• Reporter: Yuming Wang
• Created: 13/Jul/20 08:18
• Updated: 23/May/21 05:50

Description

How to reproduce this issue:

spark.range(100).createTempView("t1")
spark.range(200).createTempView("t2")
spark.sql("set spark.sql.autoBroadcastJoinThreshold=0")
spark.sql("select /*+ COALESCE(1) */ t1.* from t1 join t2 on (t1.id = t2.id)").show

The dag is:

A real case:

Issue Links

• links to: [Github] Pull Request #29120 (LantaoJin)