Fix SerDe Issue 195

src/main/java/com/yahoo/sketches/quantiles/DoublesUnionImpl.java

@@ -77,9 +77,9 @@ static DoublesUnionImpl heapifyInstance(final DoublesSketch sketch) {
    * @return a DoublesUnion object
    */
   static DoublesUnionImpl heapifyInstance(final Memory srcMem) {
-    final long n = srcMem.getLong(PreambleUtil.N_LONG);
+    final int preLongs = srcMem.getByte(PreambleUtil.PREAMBLE_LONGS_BYTE) & 0xFF;
     final int k = srcMem.getShort(PreambleUtil.K_SHORT) & 0xFFFF;
-    final HeapUpdateDoublesSketch sketch = (n == 0)
+    final HeapUpdateDoublesSketch sketch = (preLongs == 1)
         ? HeapUpdateDoublesSketch.newInstance(k)
         : HeapUpdateDoublesSketch.heapifyInstance(srcMem);
     final DoublesUnionImpl union = new DoublesUnionImpl(k);

src/test/java/com/yahoo/sketches/quantiles/DoublesUnionImplTest.java

@@ -693,6 +693,17 @@ public void isSameResourceDirect() {
     Assert.assertFalse(union.isSameResource(mem2));
   }
 
+  @SuppressWarnings("unused")
+  @Test
+  public void emptyUnionSerDeIssue195() {
+    DoublesUnion union = DoublesUnion.builder().build();
+    byte[] byteArr = union.toByteArray();
+    Memory mem = Memory.wrap(byteArr);
+    DoublesUnion union2 = DoublesUnionBuilder.heapify(mem);
+    Assert.assertEquals(mem.getCapacity(), 8L);
+    Assert.assertTrue(union2.isEmpty());
+  }
+
   @Test
   public void printlnTest() {
     println("PRINTING: " + this.getClass().getName());

src/test/java/com/yahoo/sketches/tuple/FilterTest.java

@@ -1,13 +1,14 @@
 package com.yahoo.sketches.tuple;
 
+import java.util.Random;
+
 import org.testng.Assert;
 import org.testng.annotations.Test;
 
-import java.util.Random;
-
 public class FilterTest {
 
-    private final int numberOfElements = 100;
+    private static final int numberOfElements = 100;
+    private static final Random random = new Random(1);//deterministic for this class
 
     @Test
     public void emptySketch() {
@@ -39,7 +40,8 @@ public void nullSketch() {
 
     @Test
     public void filledSketchShouldBehaveTheSame() {
-        UpdatableSketch<Double, DoubleSummary> sketch = new UpdatableSketchBuilder<>(new DoubleSummaryFactory()).build();
+        UpdatableSketch<Double, DoubleSummary> sketch =
+            new UpdatableSketchBuilder<>(new DoubleSummaryFactory()).build();
 
         fillSketch(sketch, numberOfElements, 0.0);
 
@@ -56,7 +58,8 @@ public void filledSketchShouldBehaveTheSame() {
 
     @Test
     public void filledSketchShouldFilterOutElements() {
-        UpdatableSketch<Double, DoubleSummary> sketch = new UpdatableSketchBuilder<>(new DoubleSummaryFactory()).build();
+        UpdatableSketch<Double, DoubleSummary> sketch =
+            new UpdatableSketchBuilder<>(new DoubleSummaryFactory()).build();
 
         fillSketch(sketch, numberOfElements, 0.0);
         fillSketch(sketch, 2 * numberOfElements, 1.0);
@@ -74,7 +77,8 @@ public void filledSketchShouldFilterOutElements() {
 
     @Test
     public void filteringInEstimationMode() {
-        UpdatableSketch<Double, DoubleSummary> sketch = new UpdatableSketchBuilder<>(new DoubleSummaryFactory()).build();
+        UpdatableSketch<Double, DoubleSummary> sketch =
+            new UpdatableSketchBuilder<>(new DoubleSummaryFactory()).build();
 
         int n = 10000;
         fillSketch(sketch, n, 0.0);
@@ -93,7 +97,9 @@ public void filteringInEstimationMode() {
 
     @Test
     public void nonEmptySketchWithNoEntries() {
-      UpdatableSketch<Double, DoubleSummary> sketch = new UpdatableSketchBuilder<>(new DoubleSummaryFactory()).setSamplingProbability(0.0001f).build();
+      UpdatableSketch<Double, DoubleSummary> sketch =
+          new UpdatableSketchBuilder<>(
+              new DoubleSummaryFactory()).setSamplingProbability(0.0001f).build();
       sketch.update(0, 0.0);
 
       Assert.assertFalse(sketch.isEmpty());
@@ -110,11 +116,12 @@ public void nonEmptySketchWithNoEntries() {
       Assert.assertEquals(filteredSketch.getUpperBound(1), sketch.getUpperBound(1));
     }
 
-    private static void fillSketch(UpdatableSketch<Double, DoubleSummary> sketch, int numberOfElements, Double sketchValue) {
-        Random random = new Random();
+    private static void fillSketch(UpdatableSketch<Double, DoubleSummary> sketch,
+        int numberOfElements, Double sketchValue) {
+
 
-        for (int cont = 0; cont < numberOfElements; cont++) {
-            sketch.update(random.nextLong(), sketchValue);
-        }
+      for (int cont = 0; cont < numberOfElements; cont++) {
+          sketch.update(random.nextLong(), sketchValue);
+      }
     }
 }