Save memory when auto_date_histogram is not on top

rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/330_auto_date_histogram.yml

@@ -4,6 +4,7 @@ setup:
           index: test
           body:
             settings:
+              number_of_shards: 1
               number_of_replicas: 0
             mappings:
               properties:
@@ -75,3 +76,25 @@ setup:
   - match: { aggregations.histo.buckets.1.doc_count: 2 }
   - match: { aggregations.histo.buckets.1.v.value: 7 }
   - match: { aggregations.histo_avg_v.value: 5 }
+
+---
+"profile at top level":
+  - skip:
+      version: " - 7.99.99"
+      reason: Debug information added in 8.0.0 (to be backported to 7.9.0)
+
+  - do:
+      search:
+        body:
+          profile: true
+          size: 0
+          aggs:
+            histo:
+              auto_date_histogram:
+                field: date
+                buckets: 2
+
+  - match: { hits.total.value: 4 }
+  - length: { aggregations.histo.buckets: 2 }
+  - match: { profile.shards.0.aggregations.0.type: AutoDateHistogramAggregator.FromSingle }
+  - match: { profile.shards.0.aggregations.0.debug.surviving_buckets: 4 }

server/src/main/java/org/elasticsearch/search/aggregations/bucket/BucketsAggregator.java

@@ -30,6 +30,7 @@
 import org.elasticsearch.search.aggregations.InternalAggregation;
 import org.elasticsearch.search.aggregations.InternalAggregations;
 import org.elasticsearch.search.aggregations.LeafBucketCollector;
+import org.elasticsearch.search.aggregations.bucket.global.GlobalAggregator;
 import org.elasticsearch.search.aggregations.bucket.terms.LongKeyedBucketOrds;
 import org.elasticsearch.search.aggregations.support.AggregationPath;
 import org.elasticsearch.search.internal.SearchContext;
@@ -329,7 +330,7 @@ protected final <B> InternalAggregation[] buildAggregationsForVariableBuckets(lo
      * @param bucketOrds hash of values to the bucket ordinal
      */
     protected final <B> InternalAggregation[] buildAggregationsForVariableBuckets(long[] owningBucketOrds, LongKeyedBucketOrds bucketOrds,
-            BucketBuilderForVariable<B> bucketBuilder, Function<List<B>, InternalAggregation> resultBuilder) throws IOException {
+            BucketBuilderForVariable<B> bucketBuilder, ResultBuilderForVariable<B> resultBuilder) throws IOException {
         long totalOrdsToCollect = 0;
         for (int ordIdx = 0; ordIdx < owningBucketOrds.length; ordIdx++) {
             totalOrdsToCollect += bucketOrds.bucketsInOrd(owningBucketOrds[ordIdx]);
@@ -360,14 +361,18 @@ protected final <B> InternalAggregation[] buildAggregationsForVariableBuckets(lo
                 }
                 buckets.add(bucketBuilder.build(ordsEnum.value(), bucketDocCount(ordsEnum.ord()), subAggregationResults[b++]));
             }
-            results[ordIdx] = resultBuilder.apply(buckets);
+            results[ordIdx] = resultBuilder.build(owningBucketOrds[ordIdx], buckets);
         }
         return results;
     }
     @FunctionalInterface
     protected interface BucketBuilderForVariable<B> {
         B build(long bucketValue, int docCount, InternalAggregations subAggregationResults);
     }
+    @FunctionalInterface
+    protected interface ResultBuilderForVariable<B> {
+        InternalAggregation build(long owninigBucketOrd, List<B> buckets);
+    }
 
     /**
      * Utility method to build empty aggregations of the sub aggregators.
@@ -407,4 +412,15 @@ public BucketComparator bucketComparator(String key, SortOrder order) {
                 "Either drop the key (a la \"" + name() + "\") or change it to \"doc_count\" (a la \"" + name() +
                 ".doc_count\") or \"key\".");
     }
+
+    public static boolean descendsFromGlobalAggregator(Aggregator parent) {
+        while (parent != null) {
+            if (parent.getClass() == GlobalAggregator.class) {
+                return true;
+            }
+            parent = parent.parent();
+        }
+        return false;
+    }
+
 }

server/src/main/java/org/elasticsearch/search/aggregations/bucket/DeferableBucketAggregator.java

@@ -23,7 +23,6 @@
 import org.elasticsearch.search.aggregations.AggregatorFactories;
 import org.elasticsearch.search.aggregations.BucketCollector;
 import org.elasticsearch.search.aggregations.MultiBucketCollector;
-import org.elasticsearch.search.aggregations.bucket.global.GlobalAggregator;
 import org.elasticsearch.search.internal.SearchContext;
 
 import java.io.IOException;
@@ -70,16 +69,6 @@ protected void doPreCollection() throws IOException {
         collectableSubAggregators = MultiBucketCollector.wrap(collectors);
     }
 
-    public static boolean descendsFromGlobalAggregator(Aggregator parent) {
-        while (parent != null) {
-            if (parent.getClass() == GlobalAggregator.class) {
-                return true;
-            }
-            parent = parent.parent();
-        }
-        return false;
-    }
-
     public DeferringBucketCollector getDeferringCollector() {
         // Default impl is a collector that selects the best buckets
         // but an alternative defer policy may be based on best docs.

server/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/AbstractHistogramAggregator.java

@@ -90,7 +90,7 @@ public InternalAggregation[] buildAggregations(long[] owningBucketOrds) throws I
                 double roundKey = Double.longBitsToDouble(bucketValue);
                 double key = roundKey * interval + offset;
                 return new InternalHistogram.Bucket(key, docCount, keyed, formatter, subAggregationResults);
-            }, buckets -> {
+            }, (owningBucketOrd, buckets) -> {
                 // the contract of the histogram aggregation is that shards must return buckets ordered by key in ascending order
                 CollectionUtil.introSort(buckets, BucketOrder.key(true).comparator());
 

server/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/AutoDateHistogramAggregationBuilder.java

@@ -290,6 +290,10 @@ public long getRoughEstimateDurationMillis() {
             return roughEstimateDurationMillis;
         }
 
+        public long getMaximumRoughEstimateDurationMillis() {
+            return getRoughEstimateDurationMillis() * getMaximumInnerInterval();
+        }
+
         @Override
         public int hashCode() {
             return Objects.hash(rounding, Arrays.hashCode(innerIntervals), dateTimeUnit);