Hi, DataFrame.explain() shows the physical plan of a query. I noticed there are a lot of `Exchange`s in it, like below:
Project [period#20L,categoryName#0,regionName#10,action#15,list_id#16L] ShuffledHashJoin [region#18], [regionCode#9], BuildRight Exchange (HashPartitioning [region#18], 12) Project [categoryName#0,list_id#16L,period#20L,action#15,region#18] ShuffledHashJoin [refCategoryID#3], [category#17], BuildRight Exchange (HashPartitioning [refCategoryID#3], 12) Project [categoryName#0,refCategoryID#3] PhysicalRDD [categoryName#0,familyName#1,parentRefCategoryID#2,refCategoryID#3], MapPartitionsRDD[5] at mapPartitions at SQLContext.scala:439 Exchange (HashPartitioning [category#17], 12) Project [timestamp_sec#13L AS period#20L,category#17,region#18,action#15,list_id#16L] PhysicalRDD [syslog#12,timestamp_sec#13L,timestamp_usec#14,action#15,list_id#16L,category#17,region#18,expiration_time#19], MapPartitionsRDD[16] at map at SQLContext.scala:394 Exchange (HashPartitioning [regionCode#9], 12) Project [regionName#10,regionCode#9] PhysicalRDD [cityName#4,countryCode#5,countryName#6,dptCode#7,dptName#8,regionCode#9,regionName#10,zipCode#11], MapPartitionsRDD[11] at mapPartitions at SQLContext.scala:439 I find also its class: https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/Exchange.scala. So what does it mean ? Thank you. Hao. -- View this message in context: http://apache-spark-developers-list.1001551.n3.nabble.com/SparkSQL-What-is-Exchange-in-physical-plan-for-tp12659.html Sent from the Apache Spark Developers List mailing list archive at Nabble.com. --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@spark.apache.org For additional commands, e-mail: dev-h...@spark.apache.org