[SPARK-26021][SQL] replace minus zero with zero in Platform.putDouble/Float

common/unsafe/src/main/java/org/apache/spark/unsafe/Platform.java

@@ -120,6 +120,11 @@ public static float getFloat(Object object, long offset) {
   }
 
   public static void putFloat(Object object, long offset, float value) {
+    if (Float.isNaN(value)) {
+      value = Float.NaN;
+    } else if (value == -0.0f) {
+      value = 0.0f;
+    }
     _UNSAFE.putFloat(object, offset, value);
   }
 
@@ -128,6 +133,11 @@ public static double getDouble(Object object, long offset) {
   }
 
   public static void putDouble(Object object, long offset, double value) {
+    if (Double.isNaN(value)) {
+      value = Double.NaN;
+    } else if (value == -0.0d) {
+      value = 0.0d;
+    }
     _UNSAFE.putDouble(object, offset, value);
   }
 

common/unsafe/src/test/java/org/apache/spark/unsafe/PlatformUtilSuite.java

@@ -157,4 +157,18 @@ public void heapMemoryReuse() {
     Assert.assertEquals(onheap4.size(), 1024 * 1024 + 7);
     Assert.assertEquals(obj3, onheap4.getBaseObject());
   }
+
+  @Test
+  // SPARK-26021
+  public void writeMinusZeroIsReplacedWithZero() {
+    byte[] doubleBytes = new byte[Double.BYTES];
+    byte[] floatBytes = new byte[Float.BYTES];
+    Platform.putDouble(doubleBytes, Platform.BYTE_ARRAY_OFFSET, -0.0d);
+    Platform.putFloat(floatBytes, Platform.BYTE_ARRAY_OFFSET, -0.0f);
+    double doubleFromPlatform = Platform.getDouble(doubleBytes, Platform.BYTE_ARRAY_OFFSET);
+    float floatFromPlatform = Platform.getFloat(floatBytes, Platform.BYTE_ARRAY_OFFSET);
+
+    Assert.assertEquals(Double.doubleToLongBits(0.0d), Double.doubleToLongBits(doubleFromPlatform));
+    Assert.assertEquals(Float.floatToIntBits(0.0f), Float.floatToIntBits(floatFromPlatform));
+  }
 }

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

@@ -224,9 +224,6 @@ public void setLong(int ordinal, long value) {
   public void setDouble(int ordinal, double value) {
     assertIndexIsValid(ordinal);
     setNotNullAt(ordinal);
-    if (Double.isNaN(value)) {
-      value = Double.NaN;
-    }
     Platform.putDouble(baseObject, getFieldOffset(ordinal), value);
   }
 
@@ -255,9 +252,6 @@ public void setByte(int ordinal, byte value) {
   public void setFloat(int ordinal, float value) {
     assertIndexIsValid(ordinal);
     setNotNullAt(ordinal);
-    if (Float.isNaN(value)) {
-      value = Float.NaN;
-    }
     Platform.putFloat(baseObject, getFieldOffset(ordinal), value);
   }
 

sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/codegen/UnsafeWriter.java

@@ -199,16 +199,10 @@ protected final void writeLong(long offset, long value) {
   }
 
   protected final void writeFloat(long offset, float value) {
-    if (Float.isNaN(value)) {
-      value = Float.NaN;
-    }
     Platform.putFloat(getBuffer(), offset, value);
   }
 
   protected final void writeDouble(long offset, double value) {
-    if (Double.isNaN(value)) {
-      value = Double.NaN;
-    }
     Platform.putDouble(getBuffer(), offset, value);
   }
 }

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

@@ -723,4 +723,18 @@ class DataFrameAggregateSuite extends QueryTest with SharedSQLContext {
       "grouping expressions: [current_date(None)], value: [key: int, value: string], " +
         "type: GroupBy]"))
   }
+
+  test("SPARK-26021: Double and Float 0.0/-0.0 should be equal when grouping") {
+    val colName = "i"
+    val doubles = Seq(0.0d, -0.0d, 0.0d).toDF(colName).groupBy(colName).count().collect()
+    val floats = Seq(0.0f, -0.0f, 0.0f).toDF(colName).groupBy(colName).count().collect()
+
+    assert(doubles.length == 1)
+    assert(floats.length == 1)
+    // using compare since 0.0 == -0.0 is true
+    assert(java.lang.Double.compare(doubles(0).getDouble(0), 0.0d) == 0)
+    assert(java.lang.Float.compare(floats(0).getFloat(0), 0.0f) == 0)
+    assert(doubles(0).getLong(1) == 3)
+    assert(floats(0).getLong(1) == 3)
+  }
 }

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

@@ -289,7 +289,7 @@ object QueryTest {
   def prepareRow(row: Row): Row = {
     Row.fromSeq(row.toSeq.map {
       case null => null
-      case d: java.math.BigDecimal => BigDecimal(d)
+      case bd: java.math.BigDecimal => BigDecimal(bd)
       // Equality of WrappedArray differs for AnyVal and AnyRef in Scala 2.12.2+
       case seq: Seq[_] => seq.map {
         case b: java.lang.Byte => b.byteValue
@@ -303,6 +303,9 @@ object QueryTest {
       // Convert array to Seq for easy equality check.
       case b: Array[_] => b.toSeq
       case r: Row => prepareRow(r)
+      // spark treats -0.0 as 0.0
+      case d: Double if d == -0.0d => 0.0d
+      case f: Float if f == -0.0f => 0.0f
       case o => o
     })
   }