Optimize date_historam's hard_bounds (backport of #66051) (#66061)

This allows `date_histogram`s with `hard_bounds` and `extended_bounds`
to use the "as range" style optimizations introducedin #63643. There
isn't any work to do for `exended_bounds` besides add a test. For
`hard_bounds` we have to be careful when constructing the ranges that to
filter.

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

@@ -148,9 +148,6 @@ private static FromDateRange adaptIntoRangeOrNull(
         CardinalityUpperBound cardinality,
         Map<String, Object> metadata
     ) throws IOException {
-        if (hardBounds != null || extendedBounds != null) {
-            return null;
-        }
         long[] fixedRoundingPoints = preparedRounding.fixedRoundingPoints();
         if (fixedRoundingPoints == null) {
             return null;
@@ -169,11 +166,7 @@ private static FromDateRange adaptIntoRangeOrNull(
         if (rangeSupplier == null) {
             return null;
         }
-        RangeAggregator.Range[] ranges = new RangeAggregator.Range[fixedRoundingPoints.length];
-        for (int i = 0; i < fixedRoundingPoints.length - 1; i++) {
-            ranges[i] = new RangeAggregator.Range(null, (double) fixedRoundingPoints[i], (double) fixedRoundingPoints[i + 1]);
-        }
-        ranges[ranges.length - 1] = new RangeAggregator.Range(null, (double) fixedRoundingPoints[fixedRoundingPoints.length - 1], null);
+        RangeAggregator.Range[] ranges = ranges(hardBounds, fixedRoundingPoints);
         return new DateHistogramAggregator.FromDateRange(
             parent,
             factories,
@@ -200,6 +193,27 @@ private static FromDateRange adaptIntoRangeOrNull(
         );
     }
 
+    private static RangeAggregator.Range[] ranges(LongBounds hardBounds, long[] fixedRoundingPoints) {
+        if (hardBounds == null) {
+            RangeAggregator.Range[] ranges = new RangeAggregator.Range[fixedRoundingPoints.length];
+            for (int i = 0; i < fixedRoundingPoints.length - 1; i++) {
+                ranges[i] = new RangeAggregator.Range(null, (double) fixedRoundingPoints[i], (double) fixedRoundingPoints[i + 1]);
+            }
+            ranges[ranges.length - 1] = new RangeAggregator.Range(null, (double) fixedRoundingPoints[fixedRoundingPoints.length - 1], null);
+            return ranges;
+        }
+        List<RangeAggregator.Range> ranges = new ArrayList<>(fixedRoundingPoints.length);
+        for (int i = 0; i < fixedRoundingPoints.length - 1; i++) {
+            if (hardBounds.contain(fixedRoundingPoints[i])) {
+                ranges.add(new RangeAggregator.Range(null, (double) fixedRoundingPoints[i], (double) fixedRoundingPoints[i + 1]));
+            }
+        }
+        if (hardBounds.contain(fixedRoundingPoints[fixedRoundingPoints.length - 1])) {
+            ranges.add(new RangeAggregator.Range(null, (double) fixedRoundingPoints[fixedRoundingPoints.length - 1], null));
+        }
+        return ranges.toArray(new RangeAggregator.Range[0]);
+    }
+
     private final ValuesSource.Numeric valuesSource;
     private final DocValueFormat formatter;
     private final Rounding rounding;

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

@@ -366,7 +366,7 @@ private void addEmptyBuckets(List<Bucket> list, ReduceContext reduceContext) {
         LongBounds bounds = emptyBucketInfo.bounds;
         ListIterator<Bucket> iter = list.listIterator();
 
-        // first adding all the empty buckets *before* the actual data (based on th extended_bounds.min the user requested)
+        // first adding all the empty buckets *before* the actual data (based on the extended_bounds.min the user requested)
         InternalAggregations reducedEmptySubAggs = InternalAggregations.reduce(Collections.singletonList(emptyBucketInfo.subAggregations),
                 reduceContext);
         if (bounds != null) {

server/src/test/java/org/elasticsearch/search/aggregations/bucket/histogram/DateHistogramAggregatorTests.java

@@ -36,8 +36,10 @@
 import org.elasticsearch.search.aggregations.AggregationBuilder;
 import org.elasticsearch.search.aggregations.Aggregator;
 import org.elasticsearch.search.aggregations.BucketOrder;
+import org.elasticsearch.search.aggregations.InternalAggregation.ReduceContext;
 import org.elasticsearch.search.aggregations.bucket.terms.StringTerms;
 import org.elasticsearch.search.aggregations.bucket.terms.TermsAggregationBuilder;
+import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator.PipelineTree;
 import org.elasticsearch.search.aggregations.support.AggregationContext;
 import org.elasticsearch.search.aggregations.support.AggregationInspectionHelper;
 import org.hamcrest.Matcher;
@@ -1200,9 +1202,44 @@ public void testMissingValueDoesNotUseFromRange() throws IOException {
         );
     }
 
+    public void testExtendedBoundsUsesFromRange() throws IOException {
+        aggregationImplementationChoiceTestCase(
+            aggregableDateFieldType(false, true, DateFormatter.forPattern("yyyy")),
+            org.elasticsearch.common.collect.List.of("2017", "2018"),
+            org.elasticsearch.common.collect.List.of("2016", "2017", "2018", "2019"),
+            new DateHistogramAggregationBuilder("test").field(AGGREGABLE_DATE)
+                .calendarInterval(DateHistogramInterval.YEAR)
+                .extendedBounds(new LongBounds("2016", "2019"))
+                .minDocCount(0),
+            true
+        );
+    }
+
+    public void testHardBoundsUsesFromRange() throws IOException {
+        aggregationImplementationChoiceTestCase(
+            aggregableDateFieldType(false, true, DateFormatter.forPattern("yyyy")),
+            org.elasticsearch.common.collect.List.of("2016", "2017", "2018", "2019"),
+            org.elasticsearch.common.collect.List.of("2017", "2018"),
+            new DateHistogramAggregationBuilder("test").field(AGGREGABLE_DATE)
+                .calendarInterval(DateHistogramInterval.YEAR)
+                .hardBounds(new LongBounds("2017", "2019")),
+            true
+        );
+    }
+
+    private void aggregationImplementationChoiceTestCase(
+        DateFieldMapper.DateFieldType ft,
+        List<String> data,
+        DateHistogramAggregationBuilder builder,
+        boolean usesFromRange
+    ) throws IOException {
+        aggregationImplementationChoiceTestCase(ft, data, data, builder, usesFromRange);
+    }
+
     private void aggregationImplementationChoiceTestCase(
         DateFieldMapper.DateFieldType ft,
         List<String> data,
+        List<String> resultingBucketKeys,
         DateHistogramAggregationBuilder builder,
         boolean usesFromRange
     ) throws IOException {
@@ -1227,7 +1264,14 @@ private void aggregationImplementationChoiceTestCase(
                 agg.preCollection();
                 context.searcher().search(context.query(), agg);
                 InternalDateHistogram result = (InternalDateHistogram) agg.buildTopLevel();
-                assertThat(result.getBuckets().stream().map(InternalDateHistogram.Bucket::getKeyAsString).collect(toList()), equalTo(data));
+                result = (InternalDateHistogram) result.reduce(
+                    org.elasticsearch.common.collect.List.of(result),
+                    ReduceContext.forFinalReduction(context.bigArrays(), null, context.multiBucketConsumer(), PipelineTree.EMPTY)
+                );
+                assertThat(
+                    result.getBuckets().stream().map(InternalDateHistogram.Bucket::getKeyAsString).collect(toList()),
+                    equalTo(resultingBucketKeys)
+                );
             }
         }
     }