[SPARK-9421] Fix null-handling bugs in UnsafeRow.getDouble, getFloat(), and get(ordinal, dataType)

UnsafeRow.getDouble and getFloat() return NaN when called on columns that are null, which is inconsistent with the behavior of other row classes (which is to return 0.0).

In addition, the generic get(ordinal, dataType) method should always return null for a null literal, but currently it handles nulls by calling the type-specific accessors.

This patch addresses both of these issues and adds a regression test.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #7736 from JoshRosen/unsafe-row-null-fixes and squashes the following commits:

c8eb2ee [Josh Rosen] Fix test in UnsafeRowConverterSuite
6214682 [Josh Rosen] Fixes to null handling in UnsafeRow

sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/UnsafeRow.java

@@ -239,7 +239,7 @@ public final class UnsafeRow extends MutableRow {
 
   @Override
   public Object get(int ordinal, DataType dataType) {
-    if (dataType instanceof NullType) {
+    if (isNullAt(ordinal) || dataType instanceof NullType) {
       return null;
     } else if (dataType instanceof BooleanType) {
       return getBoolean(ordinal);
@@ -313,21 +313,13 @@ public final class UnsafeRow extends MutableRow {
   @Override
   public float getFloat(int ordinal) {
     assertIndexIsValid(ordinal);
-    if (isNullAt(ordinal)) {
-      return Float.NaN;
-    } else {
-      return PlatformDependent.UNSAFE.getFloat(baseObject, getFieldOffset(ordinal));
-    }
+    return PlatformDependent.UNSAFE.getFloat(baseObject, getFieldOffset(ordinal));
   }
 
   @Override
   public double getDouble(int ordinal) {
     assertIndexIsValid(ordinal);
-    if (isNullAt(ordinal)) {
-      return Float.NaN;
-    } else {
-      return PlatformDependent.UNSAFE.getDouble(baseObject, getFieldOffset(ordinal));
-    }
+    return PlatformDependent.UNSAFE.getDouble(baseObject, getFieldOffset(ordinal));
   }
 
   @Override

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/UnsafeRowConverterSuite.scala

@@ -146,8 +146,8 @@ class UnsafeRowConverterSuite extends SparkFunSuite with Matchers {
     assert(createdFromNull.getShort(3) === 0)
     assert(createdFromNull.getInt(4) === 0)
     assert(createdFromNull.getLong(5) === 0)
-    assert(java.lang.Float.isNaN(createdFromNull.getFloat(6)))
-    assert(java.lang.Double.isNaN(createdFromNull.getDouble(7)))
+    assert(createdFromNull.getFloat(6) === 0.0f)
+    assert(createdFromNull.getDouble(7) === 0.0d)
     assert(createdFromNull.getUTF8String(8) === null)
     assert(createdFromNull.getBinary(9) === null)
     // assert(createdFromNull.get(10) === null)

sql/core/src/test/scala/org/apache/spark/sql/UnsafeRowSuite.scala

@@ -22,7 +22,7 @@ import java.io.ByteArrayOutputStream
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions.{UnsafeRow, UnsafeProjection}
-import org.apache.spark.sql.types.{DataType, IntegerType, StringType}
+import org.apache.spark.sql.types._
 import org.apache.spark.unsafe.PlatformDependent
 import org.apache.spark.unsafe.memory.MemoryAllocator
 import org.apache.spark.unsafe.types.UTF8String
@@ -67,4 +67,19 @@ class UnsafeRowSuite extends SparkFunSuite {
 
     assert(bytesFromArrayBackedRow === bytesFromOffheapRow)
   }
+
+  test("calling getDouble() and getFloat() on null columns") {
+    val row = InternalRow.apply(null, null)
+    val unsafeRow = UnsafeProjection.create(Array[DataType](FloatType, DoubleType)).apply(row)
+    assert(unsafeRow.getFloat(0) === row.getFloat(0))
+    assert(unsafeRow.getDouble(1) === row.getDouble(1))
+  }
+
+  test("calling get(ordinal, datatype) on null columns") {
+    val row = InternalRow.apply(null)
+    val unsafeRow = UnsafeProjection.create(Array[DataType](NullType)).apply(row)
+    for (dataType <- DataTypeTestUtils.atomicTypes) {
+      assert(unsafeRow.get(0, dataType) === null)
+    }
+  }
 }