[SPARK-18772][SQL] Avoid unnecessary conversion try for special floats in JSON

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/json/JacksonParser.scala

@@ -18,7 +18,6 @@
 package org.apache.spark.sql.catalyst.json
 
 import java.io.ByteArrayOutputStream
-import java.util.Locale
 
 import scala.collection.mutable.ArrayBuffer
 import scala.util.Try
@@ -126,16 +125,11 @@ class JacksonParser(
 
         case VALUE_STRING =>
           // Special case handling for NaN and Infinity.
-          val value = parser.getText
-          val lowerCaseValue = value.toLowerCase(Locale.ROOT)
-          if (lowerCaseValue.equals("nan") ||
-            lowerCaseValue.equals("infinity") ||
-            lowerCaseValue.equals("-infinity") ||
-            lowerCaseValue.equals("inf") ||
-            lowerCaseValue.equals("-inf")) {
-            value.toFloat
-          } else {
-            throw new RuntimeException(s"Cannot parse $value as FloatType.")
+          parser.getText match {
+            case "NaN" => Float.NaN
+            case "Infinity" => Float.PositiveInfinity
+            case "-Infinity" => Float.NegativeInfinity
+            case other => throw new RuntimeException(s"Cannot parse $other as FloatType.")
           }
       }
 
@@ -146,16 +140,11 @@ class JacksonParser(
 
         case VALUE_STRING =>
           // Special case handling for NaN and Infinity.
-          val value = parser.getText
-          val lowerCaseValue = value.toLowerCase(Locale.ROOT)
-          if (lowerCaseValue.equals("nan") ||
-            lowerCaseValue.equals("infinity") ||
-            lowerCaseValue.equals("-infinity") ||
-            lowerCaseValue.equals("inf") ||
-            lowerCaseValue.equals("-inf")) {
-            value.toDouble
-          } else {
-            throw new RuntimeException(s"Cannot parse $value as DoubleType.")
+          parser.getText match {
+            case "NaN" => Double.NaN
+            case "Infinity" => Double.PositiveInfinity
+            case "-Infinity" => Double.NegativeInfinity
+            case other => throw new RuntimeException(s"Cannot parse $other as DoubleType.")
           }
       }
 

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala

@@ -20,6 +20,7 @@ package org.apache.spark.sql.execution.datasources.json
 import java.io.{File, StringWriter}
 import java.nio.charset.StandardCharsets
 import java.sql.{Date, Timestamp}
+import java.util.Locale
 
 import com.fasterxml.jackson.core.JsonFactory
 import org.apache.hadoop.fs.{Path, PathFilter}
@@ -1988,4 +1989,43 @@ class JsonSuite extends QueryTest with SharedSQLContext with TestJsonData {
       assert(errMsg.startsWith("The field for corrupt records must be string type and nullable"))
     }
   }
+
+  test("SPARK-18772: Parse special floats correctly") {
+    val jsons = Seq(
+      """{"a": "NaN"}""",
+      """{"a": "Infinity"}""",
+      """{"a": "-Infinity"}""")
+
+    // positive cases
+    val checks: Seq[Double => Boolean] = Seq(
+      _.isNaN,
+      _.isPosInfinity,
+      _.isNegInfinity)
+
+    Seq(FloatType, DoubleType).foreach { dt =>
+      jsons.zip(checks).foreach { case (json, check) =>
+        val ds = spark.read
+          .schema(StructType(Seq(StructField("a", dt))))
+          .json(Seq(json).toDS())
+          .select($"a".cast(DoubleType)).as[Double]
+        assert(check(ds.first()))
+      }
+    }
+
+    // negative cases
+    Seq(FloatType, DoubleType).foreach { dt =>
+      val lowerCasedJsons = jsons.map(_.toLowerCase(Locale.ROOT))
+      // The special floats are case-sensitive so these cases below throw exceptions.
+      lowerCasedJsons.foreach { lowerCasedJson =>
+        val e = intercept[SparkException] {
+          spark.read
+            .option("mode", "FAILFAST")
+            .schema(StructType(Seq(StructField("a", dt))))
+            .json(Seq(lowerCasedJson).toDS())
+            .collect()
+        }
+        assert(e.getMessage.contains("Cannot parse"))
+      }
+    }
+  }
 }