eliminate initialization with default value

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala

@@ -321,12 +321,10 @@ case class RegExpReplace(subject: Expression, regexp: Expression, rep: Expressio
 
     val matcher = ctx.freshName("matcher")
 
-    val termLastRegex = ctx.addMutableState("UTF8String", "lastRegex", v => s"$v = null;")
-    val termPattern = ctx.addMutableState(classNamePattern, "pattern", v => s"$v = null;")
-    val termLastReplacement = ctx.addMutableState("String", "lastReplacement",
-      v => s"$v = null;")
-    val termLastReplacementInUTF8 = ctx.addMutableState("UTF8String", "lastReplacementInUTF8",
-      v => s"$v = null;")
+    val termLastRegex = ctx.addMutableState("UTF8String", "lastRegex")
+    val termPattern = ctx.addMutableState(classNamePattern, "pattern")
+    val termLastReplacement = ctx.addMutableState("String", "lastReplacement")
+    val termLastReplacementInUTF8 = ctx.addMutableState("UTF8String", "lastReplacementInUTF8")
     val termResult = ctx.addMutableState(classNameStringBuffer, "result",
       v => s"$v = new $classNameStringBuffer();")
 
@@ -414,8 +412,8 @@ case class RegExpExtract(subject: Expression, regexp: Expression, idx: Expressio
     val matcher = ctx.freshName("matcher")
     val matchResult = ctx.freshName("matchResult")
 
-    val termLastRegex = ctx.addMutableState("UTF8String", "lastRegex", v => s"$v = null;")
-    val termPattern = ctx.addMutableState(classNamePattern, "pattern", v => s"$v = null;")
+    val termLastRegex = ctx.addMutableState("UTF8String", "lastRegex")
+    val termPattern = ctx.addMutableState(classNamePattern, "pattern")
 
     val setEvNotNull = if (nullable) {
       s"${ev.isNull} = false;"

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala

@@ -534,9 +534,9 @@ case class StringTranslate(srcExpr: Expression, matchingExpr: Expression, replac
   override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
     val classNameDict = classOf[JMap[Character, Character]].getCanonicalName
 
-    val termLastMatching = ctx.addMutableState("UTF8String", "lastMatching", v => s"$v = null;")
-    val termLastReplace = ctx.addMutableState("UTF8String", "lastReplace", v => s"$v = null;")
-    val termDict = ctx.addMutableState(classNameDict, "dict", v => s"$v = null;")
+    val termLastMatching = ctx.addMutableState("UTF8String", "lastMatching")
+    val termLastReplace = ctx.addMutableState("UTF8String", "lastReplace")
+    val termDict = ctx.addMutableState(classNameDict, "dict")
 
     nullSafeCodeGen(ctx, ev, (src, matching, replace) => {
       val check = if (matchingExpr.foldable && replaceExpr.foldable) {

sql/core/src/main/scala/org/apache/spark/sql/execution/ColumnarBatchScan.scala

@@ -75,17 +75,17 @@ private[sql] trait ColumnarBatchScan extends CodegenSupport {
     // metrics
     val numOutputRows = metricTerm(ctx, "numOutputRows")
     val scanTimeMetric = metricTerm(ctx, "scanTime")
-    val scanTimeTotalNs = ctx.addMutableState(ctx.JAVA_LONG, "scanTime", v => s"$v = 0;")
+    val scanTimeTotalNs = ctx.addMutableState(ctx.JAVA_LONG, "scanTime")
 
     val columnarBatchClz = classOf[ColumnarBatch].getName
-    val batch = ctx.addMutableState(columnarBatchClz, "batch", v => s"$v = null;")
+    val batch = ctx.addMutableState(columnarBatchClz, "batch")
 
-    val idx = ctx.addMutableState(ctx.JAVA_INT, "batchIdx", v => s"$v = 0;")
+    val idx = ctx.addMutableState(ctx.JAVA_INT, "batchIdx")
     val columnVectorClzs = vectorTypes.getOrElse(
       Seq.fill(output.indices.size)(classOf[ColumnVector].getName))
     val (colVars, columnAssigns) = columnVectorClzs.zipWithIndex.map {
       case (columnVectorClz, i) =>
-        val name = ctx.addMutableState(columnVectorClz, s"colInstance$i", v => s"$v = null;")
+        val name = ctx.addMutableState(columnVectorClz, s"colInstance$i")
         (name, s"$name = ($columnVectorClz) $batch.column($i);")
     }.unzip
 

sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/HashAggregateExec.scala

@@ -178,7 +178,7 @@ case class HashAggregateExec(
   private var bufVars: Seq[ExprCode] = _
 
   private def doProduceWithoutKeys(ctx: CodegenContext): String = {
-    val initAgg = ctx.addMutableState(ctx.JAVA_BOOLEAN, "initAgg", v => s"$v = false;")
+    val initAgg = ctx.addMutableState(ctx.JAVA_BOOLEAN, "initAgg")
     // The generated function doesn't have input row in the code context.
     ctx.INPUT_ROW = null
 
@@ -565,7 +565,7 @@ case class HashAggregateExec(
   }
 
   private def doProduceWithKeys(ctx: CodegenContext): String = {
-    val initAgg = ctx.addMutableState(ctx.JAVA_BOOLEAN, "initAgg", v => s"$v = false;")
+    val initAgg = ctx.addMutableState(ctx.JAVA_BOOLEAN, "initAgg")
     if (sqlContext.conf.enableTwoLevelAggMap) {
       enableTwoLevelHashMap(ctx)
     } else {
@@ -750,7 +750,7 @@ case class HashAggregateExec(
 
     val (checkFallbackForGeneratedHashMap, checkFallbackForBytesToBytesMap, resetCounter,
     incCounter) = if (testFallbackStartsAt.isDefined) {
-      val countTerm = ctx.addMutableState(ctx.JAVA_INT, "fallbackCounter", v => s"$v = 0;")
+      val countTerm = ctx.addMutableState(ctx.JAVA_INT, "fallbackCounter")
       (s"$countTerm < ${testFallbackStartsAt.get._1}",
         s"$countTerm < ${testFallbackStartsAt.get._2}", s"$countTerm = 0;", s"$countTerm += 1;")
     } else {

sql/core/src/main/scala/org/apache/spark/sql/execution/basicPhysicalOperators.scala

@@ -363,7 +363,7 @@ case class RangeExec(range: org.apache.spark.sql.catalyst.plans.logical.Range)
   protected override def doProduce(ctx: CodegenContext): String = {
     val numOutput = metricTerm(ctx, "numOutputRows")
 
-    val initTerm = ctx.addMutableState(ctx.JAVA_BOOLEAN, "initRange", v => s"$v = false;")
+    val initTerm = ctx.addMutableState(ctx.JAVA_BOOLEAN, "initRange")
     val number = ctx.addMutableState(ctx.JAVA_LONG, "number", v => s"$v = 0L;")
 
     val value = ctx.freshName("value")
@@ -383,10 +383,10 @@ case class RangeExec(range: org.apache.spark.sql.catalyst.plans.logical.Range)
     // the metrics.
 
     // Once number == batchEnd, it's time to progress to the next batch.
-    val batchEnd = ctx.addMutableState(ctx.JAVA_LONG, "batchEnd", v => s"$v = 0;")
+    val batchEnd = ctx.addMutableState(ctx.JAVA_LONG, "batchEnd")
 
     // How many values should still be generated by this range operator.
-    val numElementsTodo = ctx.addMutableState(ctx.JAVA_LONG, "numElementsTodo", v => s"$v = 0L;")
+    val numElementsTodo = ctx.addMutableState(ctx.JAVA_LONG, "numElementsTodo")
 
     // How many values should be generated in the next batch.
     val nextBatchTodo = ctx.freshName("nextBatchTodo")

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

@@ -423,7 +423,7 @@ case class SortMergeJoinExec(
   private def genScanner(ctx: CodegenContext): (String, String) = {
     // Create class member for next row from both sides.
     val leftRow = ctx.addMutableState("InternalRow", "leftRow")
-    val rightRow = ctx.addMutableState("InternalRow", "rightRow", v => s"$v = null;")
+    val rightRow = ctx.addMutableState("InternalRow", "rightRow")
 
     // Create variables for join keys from both sides.
     val leftKeyVars = createJoinKey(ctx, leftRow, leftKeys, left.output)

sql/core/src/main/scala/org/apache/spark/sql/execution/limit.scala

@@ -71,15 +71,15 @@ trait BaseLimitExec extends UnaryExecNode with CodegenSupport {
   }
 
   override def doConsume(ctx: CodegenContext, input: Seq[ExprCode], row: ExprCode): String = {
-    val stopEarly = ctx.addMutableState(ctx.JAVA_BOOLEAN, "stopEarly", v => s"$v = false;")
+    val stopEarly = ctx.addMutableState(ctx.JAVA_BOOLEAN, "stopEarly")
 
     ctx.addNewFunction("stopEarly", s"""
       @Override
       protected boolean stopEarly() {
         return $stopEarly;
       }
     """, inlineToOuterClass = true)
-    val countTerm = ctx.addMutableState(ctx.JAVA_INT, "count", v => s"$v = 0;")
+    val countTerm = ctx.addMutableState(ctx.JAVA_INT, "count")
     s"""
        | if ($countTerm < $limit) {
        |   $countTerm += 1;