[SPARK-34702][SQL] Avoid unnecessary code generation in JoinCodegenSu…

…pport.genBuildSideVars

### What changes were proposed in this pull request?

As a followup from code review in #31736 (comment) , for `JoinCodegenSupport.genBuildSideVars`, we only need to generate build side variables with default values for LEFT OUTER and RIGHT OUTER join, but not for other join types (i.e. LEFT SEMI and LEFT ANTI). Create this PR to clean up the code.

In addition, change `BroadcastNestedLoopJoinExec` unit test to cover both whole stage code-gen enabled and disabled. Harden the unit tests to exercise all code paths.

### Why are the changes needed?

Avoid unnecessary code generation.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Existing unit tests.
* BHJ and SHJ inner join is covered in `InnerJoinSuite.scala`
* BHJ and SHJ left outer and right outer join are covered in `OuterJoinSuite.scala`
* BHJ and SHJ left semi, left anti and existence join are covered in `ExistenceJoinSuite.scala`

Closes #31802 from c21/join-codegen-fix.

Authored-by: Cheng Su <chengsu@fb.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

sql/core/src/main/scala/org/apache/spark/sql/execution/joins/JoinCodegenSupport.scala

@@ -20,7 +20,7 @@ package org.apache.spark.sql.execution.joins
 import org.apache.spark.sql.catalyst.expressions.{BindReferences, BoundReference}
 import org.apache.spark.sql.catalyst.expressions.codegen._
 import org.apache.spark.sql.catalyst.expressions.codegen.Block._
-import org.apache.spark.sql.catalyst.plans.InnerLike
+import org.apache.spark.sql.catalyst.plans.{ExistenceJoin, InnerLike, LeftAnti, LeftOuter, LeftSemi, RightOuter}
 import org.apache.spark.sql.execution.{CodegenSupport, SparkPlan}
 
 /**
@@ -73,23 +73,27 @@ trait JoinCodegenSupport extends CodegenSupport with BaseJoinExec {
     ctx.INPUT_ROW = buildRow
     buildPlan.output.zipWithIndex.map { case (a, i) =>
       val ev = BoundReference(i, a.dataType, a.nullable).genCode(ctx)
-      if (joinType.isInstanceOf[InnerLike]) {
-        ev
-      } else {
-        // the variables are needed even there is no matched rows
-        val isNull = ctx.freshName("isNull")
-        val value = ctx.freshName("value")
-        val javaType = CodeGenerator.javaType(a.dataType)
-        val code = code"""
-          |boolean $isNull = true;
-          |$javaType $value = ${CodeGenerator.defaultValue(a.dataType)};
-          |if ($buildRow != null) {
-          |  ${ev.code}
-          |  $isNull = ${ev.isNull};
-          |  $value = ${ev.value};
-          |}
-        """.stripMargin
-        ExprCode(code, JavaCode.isNullVariable(isNull), JavaCode.variable(value, a.dataType))
+      joinType match {
+        case _: InnerLike | LeftSemi | LeftAnti | _: ExistenceJoin =>
+          ev
+        case LeftOuter | RightOuter =>
+          // the variables are needed even there is no matched rows
+          val isNull = ctx.freshName("isNull")
+          val value = ctx.freshName("value")
+          val javaType = CodeGenerator.javaType(a.dataType)
+          val code = code"""
+            |boolean $isNull = true;
+            |$javaType $value = ${CodeGenerator.defaultValue(a.dataType)};
+            |if ($buildRow != null) {
+            |  ${ev.code}
+            |  $isNull = ${ev.isNull};
+            |  $value = ${ev.value};
+            |}
+          """.stripMargin
+          ExprCode(code, JavaCode.isNullVariable(isNull), JavaCode.variable(value, a.dataType))
+        case _ =>
+          throw new IllegalArgumentException(
+            s"JoinCodegenSupport.genBuildSideVars should not take $joinType as the JoinType")
       }
     }
   }

sql/core/src/test/scala/org/apache/spark/sql/execution/joins/InnerJoinSuite.scala

@@ -198,7 +198,7 @@ class InnerJoinSuite extends SparkPlanTest with SharedSparkSession {
       }
     }
 
-    test(s"$testName using BroadcastNestedLoopJoin build left") {
+    testWithWholeStageCodegenOnAndOff(s"$testName using BroadcastNestedLoopJoin build left") { _ =>
       withSQLConf(SQLConf.SHUFFLE_PARTITIONS.key -> "1") {
         checkAnswer2(leftRows, rightRows, (left: SparkPlan, right: SparkPlan) =>
           BroadcastNestedLoopJoinExec(left, right, BuildLeft, Inner, Some(condition())),
@@ -207,7 +207,7 @@ class InnerJoinSuite extends SparkPlanTest with SharedSparkSession {
       }
     }
 
-    test(s"$testName using BroadcastNestedLoopJoin build right") {
+    testWithWholeStageCodegenOnAndOff(s"$testName using BroadcastNestedLoopJoin build right") { _ =>
       withSQLConf(SQLConf.SHUFFLE_PARTITIONS.key -> "1") {
         checkAnswer2(leftRows, rightRows, (left: SparkPlan, right: SparkPlan) =>
           BroadcastNestedLoopJoinExec(left, right, BuildRight, Inner, Some(condition())),