Include minimum in equality

Author: JonasKunz

libs/exponential-histogram/src/main/java/org/elasticsearch/exponentialhistogram/ExponentialHistogram.java

@@ -153,11 +153,19 @@ static boolean equals(ExponentialHistogram a, ExponentialHistogram b) {
 
         return a.scale() == b.scale()
             && a.sum() == b.sum()
+            && equalsIncludingNaN(a.min(), b.min())
             && a.zeroBucket().equals(b.zeroBucket())
             && bucketIteratorsEqual(a.negativeBuckets().iterator(), b.negativeBuckets().iterator())
             && bucketIteratorsEqual(a.positiveBuckets().iterator(), b.positiveBuckets().iterator());
     }
 
+    private static boolean equalsIncludingNaN(double a, double b) {
+        if (Double.isNaN(a)) {
+            return Double.isNaN(b);
+        }
+        return a == b;
+    }
+
     private static boolean bucketIteratorsEqual(BucketIterator a, BucketIterator b) {
         if (a.scale() != b.scale()) {
             return false;
@@ -180,8 +188,9 @@ private static boolean bucketIteratorsEqual(BucketIterator a, BucketIterator b)
     static int hashCode(ExponentialHistogram histogram) {
         int hash = histogram.scale();
         hash = 31 * hash + Double.hashCode(histogram.sum());
-        hash = 31 * hash + histogram.zeroBucket().hashCode();
         hash = 31 * hash + Long.hashCode(histogram.valueCount());
+        hash = 31 * hash + Double.hashCode(histogram.min());
+        hash = 31 * hash + histogram.zeroBucket().hashCode();
         // we intentionally don't include the hash of the buckets here, because that is likely expensive to compute
         // instead, we assume that the value count and sum are a good enough approximation in most cases to minimize collisions
         // the value count is typically available as a cached value and doesn't involve iterating over all buckets

libs/exponential-histogram/src/test/java/org/elasticsearch/exponentialhistogram/ExponentialHistogramEqualityTests.java

@@ -40,6 +40,7 @@ public class ExponentialHistogramEqualityTests extends ExponentialHistogramTestC
     public enum Modification {
         SCALE,
         SUM,
+        MIN,
         ZERO_THRESHOLD,
         ZERO_COUNT,
         POSITIVE_BUCKETS,
@@ -80,7 +81,7 @@ public void testHashQuality() {
     }
 
     private ExponentialHistogram randomHistogram() {
-        return createAutoReleasedHistogram(randomIntBetween(1, 20), randomDoubles(randomIntBetween(0, 200)).toArray());
+        return createAutoReleasedHistogram(randomIntBetween(4, 20), randomDoubles(randomIntBetween(0, 200)).toArray());
     }
 
     private ExponentialHistogram copyWithModification(ExponentialHistogram toCopy, Modification modification) {
@@ -96,6 +97,11 @@ private ExponentialHistogram copyWithModification(ExponentialHistogram toCopy, M
         } else {
             copy.setSum(toCopy.sum());
         }
+        if (modification == Modification.MIN) {
+            copy.setMin(randomDouble());
+        } else {
+            copy.setMin(toCopy.min());
+        }
         long zeroCount = toCopy.zeroBucket().count();
         double zeroThreshold = toCopy.zeroBucket().zeroThreshold();
         if (modification == Modification.ZERO_COUNT) {
@@ -144,7 +150,7 @@ private void insertRandomBucket(List<Long> indices, List<Long> counts) {
         do {
             newIndex = randomLongBetween(Math.max(MIN_INDEX, minIndex - 10), Math.min(MAX_INDEX, maxIndex + 10));
         } while (indices.contains(newIndex));
-        int position = Collections.binarySearch(indices, newIndex) + 1;
+        int position = -(Collections.binarySearch(indices, newIndex) + 1);
         indices.add(position, newIndex);
         counts.add(position, randomLongBetween(1, Long.MAX_VALUE));
     }

libs/exponential-histogram/src/test/java/org/elasticsearch/exponentialhistogram/ExponentialHistogramUtilsTests.java

@@ -113,7 +113,7 @@ public void testMinimumEstimation() {
             ExponentialHistogram histo = createAutoReleasedHistogram(bucketCount, values);
 
             OptionalDouble estimatedMin = ExponentialHistogramUtils.estimateMin(
-                new ZeroBucket(zeroThreshold, zeroValueCount),
+                ZeroBucket.create(zeroThreshold, zeroValueCount),
                 histo.negativeBuckets(),
                 histo.positiveBuckets()
             );