[GitHub] [spark] maropu commented on a change in pull request #32528: [SPARK-35350][SQL] Add code-gen for left semi sort merge join

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maropu commented on a change in pull request #32528:
URL: https://github.com/apache/spark/pull/32528#discussion_r631525737



##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/SortMergeJoinExec.scala
##########
@@ -724,9 +749,32 @@ case class SortMergeJoinExec(
        """.stripMargin
     }
 
+    lazy val semiJoin = {

Review comment:
       How about extracting this block as a private method like `codegenXXXX` 
just like `HashJoin`?

##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/SortMergeJoinExec.scala
##########
@@ -424,8 +424,18 @@ case class SortMergeJoinExec(
     // A list to hold all matched rows from buffered side.
     val clsName = classOf[ExternalAppendOnlyUnsafeRowArray].getName
 
+    // Flag to only buffer first matched row, to avoid buffering unnecessary 
rows.
+    val onlyBufferFirstMatchedRow = (joinType, condition) match {
+      case (LeftSemi, None) => true
+      case _ => false
+    }
+    val inMemoryThreshold =
+      if (onlyBufferFirstMatchedRow) {

Review comment:
       How about moving this branch into the `getInMemoryThreshold` side?
   ```
   
     // Flag to only buffer first matched row, to avoid buffering unnecessary 
rows.
     private lazy val onlyBufferFirstMatchedRow = (joinType, condition) match {
       case (LeftSemi, None) => true
       case _ => false
     }
   
     private def getInMemoryThreshold: Int = {
       if (onlyBufferFirstMatchedRow) {
         1
       } else {
         sqlContext.conf.sortMergeJoinExecBufferInMemoryThreshold
       }
     }
   ```




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