[GitHub] [spark] maropu commented on a change in pull request #31874: [SPARK-34708][SQL] Code-gen for left semi/anti broadcast nested loop join (build right side)

[GitBox <gi...@apache.org>]

maropu commented on a change in pull request #31874:
URL: https://github.com/apache/spark/pull/31874#discussion_r597347839



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/joins/BroadcastNestedLoopJoinExec.scala
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@@ -452,4 +457,50 @@ case class BroadcastNestedLoopJoinExec(
        |}
      """.stripMargin
   }
+
+  private def codegenLeftExistence(
+      ctx: CodegenContext,
+      input: Seq[ExprCode],
+      exists: Boolean): String = {
+    val (buildRowArray, buildRowArrayTerm) = prepareBroadcast(ctx)
+    val numOutput = metricTerm(ctx, "numOutputRows")
+
+    if (condition.isEmpty) {
+      if (buildRowArray.nonEmpty == exists) {
+        // Return streamed side if join condition is empty and
+        // 1. build side is non-empty for LeftSemi join
+        // or
+        // 2. build side is empty for LeftAnti join.
+        s"""
+           |$numOutput.add(1);
+           |${consume(ctx, input)}
+         """.stripMargin
+      } else {
+        // Return nothing if join condition is empty and
+        // 1. build side is empty for LeftSemi join
+        // or
+        // 2. build side is non-empty for LeftAnti join.
+        ""
+      }

Review comment:
       For this case, we don't need to add a mutable state for `buildRowArrayTerm `?




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