SparkSQL中的三种Join及其实现(broadcast join、shuffle hash join和sort merge join),程序员大本营,技术文章内容聚合第一站。
In a broadcast join, all of the selected records of one file are sent or broadcast to all the nodes of the other file before the join is performed. This is the join method that is used for all nonequijoin queries. This method is also used when the join criteria uses fields that have...
其中plan.stats.sizeInBytes <= conf.autoBroadcastJoinThreshold要求当表的大小小于conf.autoBroadcastJoinThreshold时它才可以被broadcast。conf.autoBroadcastJoinThreshold 对应 spark.sql.autoBroadcastJoinThreshold 参数。 是否选择BHJ、join的哪一边被广播综合决定于 join type (equi-join、哪一边是build side)和 join...
所以在spark UI上有时候能看到broadcast 的datasize有50M甚至100多M,而明明broadcast的阈值是10M,却变成了BroadCastHashJoin。 结论 所以在大数据量,以及在复杂的sql情况下,禁止broadcasthashjoin是明确的选择,毕竟稳是一切运行的条件,但是也是可以根据单个任务个别开启。©著作权归作者所有,转载或内容合作请联系作者 5...
spark rdd join spark rdd join会自动broadcast 背景 Spark在判断能否转为BroadCastJoin时主要是根据输入表的大小是否超过了 spark.sql.autoBroadcastJoinThreshold 参数所配置的大小,如果未超过阈值则可以转为BroadCastJoin. 结论 先说下整个判断的流程: 1.首先在非分区表情况下并且 spark.sql.statistics.fallBackToHdfs...
Broadcast join is an optimization technique in the PySpark SQL engine that is used to join two DataFrames. This technique is ideal for joining a large
SparkSQL性能调整 SparkSQL 优化 1.广播JOIN表 spark.sql.autoBroadcastJoinThreshold,默认10485760(10M) 在内存够用的情况下提高其大小,可以将join中的较小的表广播出去,而不用进行网络数据传输. 2.合理配置spark.sql.shuffle.partition设置shuffle并行度;
简介:spark在生产中是否要禁止掉BHJ(BroadcastHashJoin) 背景 本文基于spark3.2 driver内存2G 问题描述 在基于复杂的sql运行中,或者说是存在多个join操作的sql中,如果说driver内存不是很大的情况下,我们经常会遇到如下报错: Caused by: org.apache.spark.SparkException: Could not execute broadcast in 800 secs. You...
-uroot -p520462 -Dtest<E:\test.sql //mysql -u账号 -p密码 -D数据库名 < sql ...
from pyspark.sql.functions import broadcast # Assume transactions and users are DataFrames joined_df = transactions.join(broadcast(users), transactions.user_id == users.id) In this scenario, the entire users DataFrame is broadcasted to all nodes in the cluster. This means every node has a fu...