Unit test for very large percentile aggs

server/src/test/java/org/elasticsearch/search/aggregations/metrics/TDigestStateTests.java

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+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.search.aggregations.metrics;
+
+import org.elasticsearch.test.ESTestCase;
+
+import java.util.Arrays;
+
+public class TDigestStateTests extends ESTestCase {
+
+    public void testMoreThan4BValues() {
+        // Regression test for #19528
+        // See https://github.com/tdunning/t-digest/pull/70/files#diff-4487072cee29b939694825647928f742R439
+        TDigestState digest = new TDigestState(100);
+        for (int i = 0; i < 1000; ++i) {
+            digest.add(randomDouble());
+        }
+        final int count = 1 << 29;
+        for (int i = 0; i < 10; ++i) {
+            digest.add(randomDouble(), count);
+        }
+        assertEquals(1000 + 10L * (1 << 29), digest.size());
+        assertTrue(digest.size() > 2 * Integer.MAX_VALUE);
+        final double[] quantiles = new double[] { 0, 0.1, 0.5, 0.9, 1, randomDouble()};
+        Arrays.sort(quantiles);
+        double prev = Double.NEGATIVE_INFINITY;
+        for (double q : quantiles) {
+            final double v = digest.quantile(q);
+            logger.trace("q=" + q + ", v=" + v);
+            assertTrue(v >= prev);
+            assertTrue("Unexpectedly low value: " + v, v >= 0.0);
+            assertTrue("Unexpectedly high value: " + v, v <= 1.0);
+            prev = v;
+        }
+    }
+}