diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
index c4e5b844299a6..190c5bc416940 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
@@ -57,20 +57,70 @@ case class If(predicate: Expression, trueValue: Expression, falseValue: Expressi
     val trueEval = trueValue.gen(ctx)
     val falseEval = falseValue.gen(ctx)
 
-    s"""
-      ${condEval.code}
-      boolean ${ev.isNull} = false;
-      ${ctx.javaType(dataType)} ${ev.value} = ${ctx.defaultValue(dataType)};
-      if (!${condEval.isNull} && ${condEval.value}) {
-        ${trueEval.code}
-        ${ev.isNull} = ${trueEval.isNull};
-        ${ev.value} = ${trueEval.value};
-      } else {
-        ${falseEval.code}
-        ${ev.isNull} = ${falseEval.isNull};
-        ${ev.value} = ${falseEval.value};
-      }
-    """
+    // place generated code of condition, true value and false value in separate methods if
+    // their code combined is large
+    val combinedLength = condEval.code.length + trueEval.code.length + falseEval.code.length
+    if (combinedLength > 1024) {
+      val (condFuncName, condGlobalIsNull, condGlobalValue) =
+        createAndAddFunction(ctx, condEval, predicate.dataType, "evalIfCondExpr")
+      val (trueFuncName, trueGlobalIsNull, trueGlobalValue) =
+        createAndAddFunction(ctx, trueEval, trueValue.dataType, "evalIfTrueExpr")
+      val (falseFuncName, falseGlobalIsNull, falseGlobalValue) =
+        createAndAddFunction(ctx, falseEval, falseValue.dataType, "evalIfFalseExpr")
+      s"""
+        $condFuncName(${ctx.INPUT_ROW});
+        boolean ${ev.isNull} = false;
+        ${ctx.javaType(dataType)} ${ev.value} = ${ctx.defaultValue(dataType)};
+        if (!$condGlobalIsNull && $condGlobalValue) {
+          $trueFuncName(${ctx.INPUT_ROW});
+          ${ev.isNull} = $trueGlobalIsNull;
+          ${ev.value} = $trueGlobalValue;
+        } else {
+          $falseFuncName(${ctx.INPUT_ROW});
+          ${ev.isNull} = $falseGlobalIsNull;
+          ${ev.value} = $falseGlobalValue;
+        }
+      """
+    }
+    else {
+      s"""
+        ${condEval.code}
+        boolean ${ev.isNull} = false;
+        ${ctx.javaType(dataType)} ${ev.value} = ${ctx.defaultValue(dataType)};
+        if (!${condEval.isNull} && ${condEval.value}) {
+          ${trueEval.code}
+          ${ev.isNull} = ${trueEval.isNull};
+          ${ev.value} = ${trueEval.value};
+        } else {
+          ${falseEval.code}
+          ${ev.isNull} = ${falseEval.isNull};
+          ${ev.value} = ${falseEval.value};
+        }
+      """
+    }
+  }
+
+  private def createAndAddFunction(
+      ctx: CodeGenContext,
+      ev: GeneratedExpressionCode,
+      dataType: DataType,
+      baseFuncName: String): (String, String, String) = {
+    val globalIsNull = ctx.freshName("isNull")
+    ctx.addMutableState("boolean", globalIsNull, s"$globalIsNull = false;")
+    val globalValue = ctx.freshName("value")
+    ctx.addMutableState(ctx.javaType(dataType), globalValue,
+      s"$globalValue = ${ctx.defaultValue(dataType)};")
+    val funcName = ctx.freshName(baseFuncName)
+    val funcBody =
+      s"""
+         |private void $funcName(InternalRow ${ctx.INPUT_ROW}) {
+         |  ${ev.code.trim}
+         |  $globalIsNull = ${ev.isNull};
+         |  $globalValue = ${ev.value};
+         |}
+         """.stripMargin
+    ctx.addNewFunction(funcName, funcBody)
+    (funcName, globalIsNull, globalValue)
   }
 
   override def toString: String = s"if ($predicate) $trueValue else $falseValue"
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects.scala
index f4b0cdc4c7b74..aaa5b859d76f5 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects.scala
@@ -414,6 +414,8 @@ case class MapObjects private(
   override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): String = {
     val javaType = ctx.javaType(dataType)
     val elementJavaType = ctx.javaType(loopVar.dataType)
+    ctx.addMutableState("boolean", loopVar.isNull, "")
+    ctx.addMutableState(elementJavaType, loopVar.value, "")
     val genInputData = inputData.gen(ctx)
     val genFunction = lambdaFunction.gen(ctx)
     val dataLength = ctx.freshName("dataLength")
@@ -434,9 +436,9 @@ case class MapObjects private(
     }
 
     val loopNullCheck = if (primitiveElement) {
-      s"boolean ${loopVar.isNull} = ${genInputData.value}.isNullAt($loopIndex);"
+      s"${loopVar.isNull} = ${genInputData.value}.isNullAt($loopIndex);"
     } else {
-      s"boolean ${loopVar.isNull} = ${genInputData.isNull} || ${loopVar.value} == null;"
+      s"${loopVar.isNull} = ${genInputData.isNull} || ${loopVar.value} == null;"
     }
 
     s"""
@@ -452,7 +454,7 @@ case class MapObjects private(
 
         int $loopIndex = 0;
         while ($loopIndex < $dataLength) {
-          $elementJavaType ${loopVar.value} =
+          ${loopVar.value} =
             ($elementJavaType)${genInputData.value}${itemAccessor(loopIndex)};
           $loopNullCheck
 
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CodeGenerationSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CodeGenerationSuite.scala
index e35a1b2d7c9a4..030c99c5489e3 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CodeGenerationSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CodeGenerationSuite.scala
@@ -80,6 +80,21 @@ class CodeGenerationSuite extends SparkFunSuite with ExpressionEvalHelper {
     assert(actual(0) == cases)
   }
 
+  test("SPARK-18091: split large if expressions into blocks due to JVM code size limit") {
+    var strExpr: Expression = Literal("abc")
+    for (_ <- 1 to 100) {
+      strExpr = Decode(Encode(strExpr, "utf-8"), "utf-8")
+    }
+
+    val expressions = Seq(If(EqualTo(strExpr, strExpr), strExpr, strExpr))
+    val plan = GenerateMutableProjection.generate(expressions)()
+    val actual = plan(null).toSeq(expressions.map(_.dataType))
+    val expected = Seq(UTF8String.fromString("abc"))
+
+    if (!checkResult(actual, expected)) {
+      fail(s"Incorrect Evaluation: expressions: $expressions, actual: $actual, expected: $expected")
+    }
+  }
 
   test("test generated safe and unsafe projection") {
     val schema = new StructType(Array(
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala
index baa258ad26152..f376c2b7a4848 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala
@@ -1464,4 +1464,18 @@ class JsonSuite extends QueryTest with SharedSQLContext with TestJsonData {
     }
   }
 
+  test("wide nested json table") {
+    val nested = (1 to 100).map { i =>
+      s"""
+         |"c$i": $i
+       """.stripMargin
+    }.mkString(", ")
+    val json = s"""
+                  |{"a": [{$nested}], "b": [{$nested}]}
+     """.stripMargin
+    val rdd = sqlContext.sparkContext.makeRDD(Seq(json))
+    val df = sqlContext.read.json(rdd)
+    assert(df.schema.size === 2)
+    df.collect()
+  }
 }