[
https://issues.apache.org/jira/browse/SPARK-36877?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17427087#comment-17427087
]
Wenchen Fan commented on SPARK-36877:
-------------------------------------
> Should calling df.rdd trigger actual job execution when AQE is enabled?
We should. Getting RDD means the physical plan is finalized. With AQE,
finalizing the physical plan means running all the query stages except for the
last stage.
> Calling ds.rdd with AQE enabled leads to jobs being run, eventually causing
> reruns
> ----------------------------------------------------------------------------------
>
> Key: SPARK-36877
> URL: https://issues.apache.org/jira/browse/SPARK-36877
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 3.1.2, 3.2.1
> Reporter: Shardul Mahadik
> Priority: Major
> Attachments: Screen Shot 2021-09-28 at 09.32.20.png
>
>
> In one of our jobs we perform the following operation:
> {code:scala}
> val df = /* some expensive multi-table/multi-stage join */
> val numPartitions = df.rdd.getNumPartitions
> df.repartition(x).write.....
> {code}
> With AQE enabled, we found that the expensive stages were being run twice
> causing significant performance regression after enabling AQE; once when
> calling {{df.rdd}} and again when calling {{df.write}}.
> A more concrete example:
> {code:scala}
> scala> sql("SET spark.sql.adaptive.enabled=true")
> res0: org.apache.spark.sql.DataFrame = [key: string, value: string]
> scala> sql("SET spark.sql.autoBroadcastJoinThreshold=-1")
> res1: org.apache.spark.sql.DataFrame = [key: string, value: string]
> scala> val df1 = spark.range(10).withColumn("id2", $"id")
> df1: org.apache.spark.sql.DataFrame = [id: bigint, id2: bigint]
> scala> val df2 = df1.join(spark.range(10), "id").join(spark.range(10),
> "id").join(spark.range(10), "id")
> df2: org.apache.spark.sql.DataFrame = [id: bigint, id2: bigint]
> scala> val df3 = df2.groupBy("id2").count()
> df3: org.apache.spark.sql.DataFrame = [id2: bigint, count: bigint]
> scala> df3.rdd.getNumPartitions
> res2: Int = 10 (0 + 16) /
> 16]
> scala> df3.repartition(5).write.mode("overwrite").orc("/tmp/orc1")
> {code}
> In the screenshot below, you can see that the first 3 stages (0 to 4) were
> rerun again (5 to 9).
> I have two questions:
> 1) Should calling df.rdd trigger actual job execution when AQE is enabled?
> 2) Should calling df.write later cause rerun of the stages? If df.rdd has
> already partially executed the stages, shouldn't it reuse the result from
> previous stages?
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org
For additional commands, e-mail: issues-h...@spark.apache.org
