cloud-fan commented on a change in pull request #26289:
[SPARK-28560][SQL][followup] support the build side to local shuffle reader as
far as possible in BroadcastHashJoin
URL: https://github.com/apache/spark/pull/26289#discussion_r340456097
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/OptimizeLocalShuffleReader.scala
##########
@@ -27,26 +27,46 @@ import
org.apache.spark.sql.execution.exchange.{EnsureRequirements, ShuffleExcha
import org.apache.spark.sql.execution.joins.{BroadcastHashJoinExec, BuildLeft,
BuildRight}
import org.apache.spark.sql.internal.SQLConf
+/**
+ * A rule to optimize the shuffle reader to local reader as far as possible
+ * when converting the 'SortMergeJoinExec' to 'BroadcastHashJoinExec' in
runtime.
+ *
+ * This rule can be divided into two steps:
+ * Step1: Add the local reader in probe side adn then check whether additional
+ * shuffle introduced. If introduced, we will revert all the local
+ * reader in probe side.
+ * Step2: Add the local reader in build side and will not check whether
+ * additional shuffle introduced.Because the build side will not
introduce
Review comment:
nit: space after `... introduce.`
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