T digest field mapper

libs/tdigest/src/test/java/org/elasticsearch/tdigest/BigCountTests.java

@@ -21,10 +21,12 @@
 
 package org.elasticsearch.tdigest;
 
+import static org.hamcrest.Matchers.lessThanOrEqualTo;
+
 public abstract class BigCountTests extends TDigestTestCase {
 
     public void testBigMerge() {
-        try (TDigest digest = createDigest()) {
+        try (TDigest digest = createDigest(100)) {
             for (int i = 0; i < 5; i++) {
                 try (TDigest digestToMerge = getDigest()) {
                     digest.add(digestToMerge);
@@ -35,13 +37,25 @@ public void testBigMerge() {
         }
     }
 
+    /**
+     * Verify that, at a range of compression values, the size of the produced digest is not much larger than 10 times the compression
+     */
+    public void testCompression() {
+        for (int compression : new int[] { 100, 500, 1000, 10000 }) {
+            try (TDigest digest = createDigest(compression)) {
+                addData(digest);
+                assertThat("Compression = " + compression, digest.centroidCount(), lessThanOrEqualTo(compression * 10));
+            }
+        }
+    }
+
     private TDigest getDigest() {
-        TDigest digest = createDigest();
+        TDigest digest = createDigest(100);
         addData(digest);
         return digest;
     }
 
-    public TDigest createDigest() {
+    public TDigest createDigest(int compression) {
         throw new IllegalStateException("Should have over-ridden createDigest");
     }
 

libs/tdigest/src/test/java/org/elasticsearch/tdigest/BigCountTestsMergingDigestTests.java

@@ -23,7 +23,7 @@
 
 public class BigCountTestsMergingDigestTests extends BigCountTests {
     @Override
-    public TDigest createDigest() {
-        return TDigest.createMergingDigest(arrays(), 100);
+    public TDigest createDigest(int compression) {
+        return TDigest.createMergingDigest(arrays(), compression);
     }
 }

libs/tdigest/src/test/java/org/elasticsearch/tdigest/BigCountTestsTreeDigestTests.java

@@ -23,7 +23,7 @@
 
 public class BigCountTestsTreeDigestTests extends BigCountTests {
     @Override
-    public TDigest createDigest() {
-        return TDigest.createAvlTreeDigest(arrays(), 100);
+    public TDigest createDigest(int compression) {
+        return TDigest.createAvlTreeDigest(arrays(), compression);
     }
 }

server/src/main/java/org/elasticsearch/search/aggregations/metrics/TDigestState.java

@@ -42,7 +42,7 @@ public class TDigestState implements Releasable, Accountable {
     private final TDigest tdigest;
 
     // Supported tdigest types.
-    protected enum Type {
+    public enum Type {
         HYBRID,
         AVL_TREE,
         MERGING,

x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/AnalyticsPlugin.java

@@ -23,6 +23,7 @@
 import org.elasticsearch.xpack.analytics.cumulativecardinality.CumulativeCardinalityPipelineAggregationBuilder;
 import org.elasticsearch.xpack.analytics.cumulativecardinality.InternalSimpleLongValue;
 import org.elasticsearch.xpack.analytics.mapper.HistogramFieldMapper;
+import org.elasticsearch.xpack.analytics.mapper.TDigestFieldMapper;
 import org.elasticsearch.xpack.analytics.movingPercentiles.MovingPercentilesPipelineAggregationBuilder;
 import org.elasticsearch.xpack.analytics.multiterms.InternalMultiTerms;
 import org.elasticsearch.xpack.analytics.multiterms.MultiTermsAggregationBuilder;
@@ -140,6 +141,14 @@ public List<Setting<?>> getSettings() {
 
     @Override
     public Map<String, Mapper.TypeParser> getMappers() {
+        if (TDigestFieldMapper.TDIGEST_FIELD_MAPPER.isEnabled()) {
+            return Map.of(
+                HistogramFieldMapper.CONTENT_TYPE,
+                HistogramFieldMapper.PARSER,
+                TDigestFieldMapper.CONTENT_TYPE,
+                TDigestFieldMapper.PARSER
+            );
+        }
         return Map.of(HistogramFieldMapper.CONTENT_TYPE, HistogramFieldMapper.PARSER);
     }