New GeoHexGrid aggregation (#82924)

This commit introduces a new geogrid aggregation called GeoHexGridAggregation that
is based in Uber h3 grid. It only supports geo_point fields.

docs/changelog/82924.yaml

@@ -0,0 +1,5 @@
+pr: 82924
+summary: New `GeoHexGrid` aggregation
+area: Geo
+type: feature
+issues: []

docs/reference/aggregations/bucket.asciidoc

@@ -40,6 +40,8 @@ include::bucket/geodistance-aggregation.asciidoc[]
 
 include::bucket/geohashgrid-aggregation.asciidoc[]
 
+include::bucket/geohexgrid-aggregation.asciidoc[]
+
 include::bucket/geotilegrid-aggregation.asciidoc[]
 
 include::bucket/global-aggregation.asciidoc[]

docs/reference/aggregations/bucket/geohexgrid-aggregation.asciidoc

@@ -0,0 +1,249 @@
+[role="xpack"]
+[[search-aggregations-bucket-geohexgrid-aggregation]]
+=== Geohex grid aggregation
+++++
+<titleabbrev>Geohex grid</titleabbrev>
+++++
+
+A multi-bucket aggregation that groups <<geo-point,`geo_point`>>
+values into buckets that represent a grid.
+The resulting grid can be sparse and only
+contains cells that have matching data. Each cell corresponds to a
+https://h3geo.org/docs/core-library/h3Indexing#h3-cell-indexp[H3 cell index] and is
+labeled using the https://h3geo.org/docs/core-library/h3Indexing#h3index-representation[H3Index representation].
+
+See https://h3geo.org/docs/core-library/restable[the table of cell areas for H3
+resolutions] on how precision (zoom) correlates to size on the ground.
+Precision for this aggregation can be between 0 and 15, inclusive.
+
+WARNING: High-precision requests can be very expensive in terms of RAM and
+result sizes. For example, the highest-precision geohex with a precision of 15
+produces cells that cover less than 10cm by 10cm. We recommend you use a
+filter to limit high-precision requests to a smaller geographic area. For an example,
+refer to <<geohexgrid-high-precision>>.
+
+[[geohexgrid-low-precision]]
+==== Simple low-precision request
+
+[source,console,id=geohexgrid-aggregation-example]
+--------------------------------------------------
+PUT /museums
+{
+  "mappings": {
+    "properties": {
+      "location": {
+        "type": "geo_point"
+      }
+    }
+  }
+}
+
+POST /museums/_bulk?refresh
+{"index":{"_id":1}}
+{"location": "52.374081,4.912350", "name": "NEMO Science Museum"}
+{"index":{"_id":2}}
+{"location": "52.369219,4.901618", "name": "Museum Het Rembrandthuis"}
+{"index":{"_id":3}}
+{"location": "52.371667,4.914722", "name": "Nederlands Scheepvaartmuseum"}
+{"index":{"_id":4}}
+{"location": "51.222900,4.405200", "name": "Letterenhuis"}
+{"index":{"_id":5}}
+{"location": "48.861111,2.336389", "name": "Musée du Louvre"}
+{"index":{"_id":6}}
+{"location": "48.860000,2.327000", "name": "Musée d'Orsay"}
+
+POST /museums/_search?size=0
+{
+  "aggregations": {
+    "large-grid": {
+      "geohex_grid": {
+        "field": "location",
+        "precision": 4
+      }
+    }
+  }
+}
+--------------------------------------------------
+
+Response:
+
+[source,console-result]
+--------------------------------------------------
+{
+  ...
+  "aggregations": {
+    "large-grid": {
+      "buckets": [
+        {
+          "key": "841969dffffffff",
+          "doc_count": 3
+        },
+        {
+          "key": "841fb47ffffffff",
+          "doc_count": 2
+        },
+        {
+          "key": "841fa4dffffffff",
+          "doc_count": 1
+        }
+      ]
+    }
+  }
+}
+--------------------------------------------------
+// TESTRESPONSE[s/\.\.\./"took": $body.took,"_shards": $body._shards,"hits":$body.hits,"timed_out":false,/]
+
+[[geohexgrid-high-precision]]
+==== High-precision requests
+
+When requesting detailed buckets (typically for displaying a "zoomed in" map),
+a filter like <<query-dsl-geo-bounding-box-query,geo_bounding_box>> should be
+applied to narrow the subject area. Otherwise, potentially millions of buckets
+will be created and returned.
+
+[source,console,id=geohexgrid-high-precision-ex]
+--------------------------------------------------
+POST /museums/_search?size=0
+{
+  "aggregations": {
+    "zoomed-in": {
+      "filter": {
+        "geo_bounding_box": {
+          "location": {
+            "top_left": "52.4, 4.9",
+            "bottom_right": "52.3, 5.0"
+          }
+        }
+      },
+      "aggregations": {
+        "zoom1": {
+          "geohex_grid": {
+            "field": "location",
+            "precision": 12
+          }
+        }
+      }
+    }
+  }
+}
+--------------------------------------------------
+// TEST[continued]
+
+Response:
+
+[source,console-result]
+--------------------------------------------------
+{
+  ...
+  "aggregations": {
+    "zoomed-in": {
+      "doc_count": 3,
+      "zoom1": {
+        "buckets": [
+          {
+            "key": "8c1969c9b2617ff",
+            "doc_count": 1
+          },
+          {
+            "key": "8c1969526d753ff",
+            "doc_count": 1
+          },
+          {
+            "key": "8c1969526d26dff",
+            "doc_count": 1
+          }
+        ]
+      }
+    }
+  }
+}
+--------------------------------------------------
+// TESTRESPONSE[s/\.\.\./"took": $body.took,"_shards": $body._shards,"hits":$body.hits,"timed_out":false,/]
+
+[[geohexgrid-addtl-bounding-box-filtering]]
+==== Requests with additional bounding box filtering
+
+The `geohex_grid` aggregation supports an optional `bounds` parameter
+that restricts the cells considered to those that intersect the
+provided bounds. The `bounds` parameter accepts the same
+<<query-dsl-geo-bounding-box-query-accepted-formats,bounding box formats>>
+as the geo-bounding box query. This bounding box can be used with or
+without an additional `geo_bounding_box` query for filtering the points prior to aggregating.
+It is an independent bounding box that can intersect with, be equal to, or be disjoint
+to any additional `geo_bounding_box` queries defined in the context of the aggregation.
+
+[source,console,id=geohexgrid-aggregation-with-bounds]
+--------------------------------------------------
+POST /museums/_search?size=0
+{
+  "aggregations": {
+    "tiles-in-bounds": {
+      "geohex_grid": {
+        "field": "location",
+        "precision": 12,
+        "bounds": {
+          "top_left": "52.4, 4.9",
+          "bottom_right": "52.3, 5.0"
+        }
+      }
+    }
+  }
+}
+--------------------------------------------------
+// TEST[continued]
+
+Response:
+
+[source,console-result]
+--------------------------------------------------
+{
+  ...
+  "aggregations": {
+    "tiles-in-bounds": {
+      "buckets": [
+        {
+          "key": "8c1969c9b2617ff",
+          "doc_count": 1
+        },
+        {
+          "key": "8c1969526d753ff",
+          "doc_count": 1
+        },
+        {
+          "key": "8c1969526d26dff",
+          "doc_count": 1
+        }
+      ]
+    }
+  }
+}
+--------------------------------------------------
+// TESTRESPONSE[s/\.\.\./"took": $body.took,"_shards": $body._shards,"hits":$body.hits,"timed_out":false,/]
+
+[[geohexgrid-options]]
+==== Options
+
+[horizontal]
+field::
+(Required, string) Field containing indexed geo-point values. Must be explicitly
+mapped as a <<geo-point,`geo_point`>> field. If the field contains an array,
+`geohex_grid` aggregates all array values.
+
+precision::
+(Optional, integer) Integer zoom of the key used to define cells/buckets in
+the results. Defaults to `6`. Values outside of [`0`,`15`] will be rejected.
+
+bounds::
+(Optional, object) Bounding box used to filter the geo-points in each bucket.
+Accepts the same bounding box formats as the
+<<query-dsl-geo-bounding-box-query-accepted-formats,geo-bounding box query>>.
+
+size::
+(Optional, integer) Maximum number of buckets to return. Defaults to 10,000.
+When results are trimmed, buckets are prioritized based on the volume of
+documents they contain.
+
+shard_size::
+(Optional, integer) Number of buckets returned from each shard. Defaults to
+`max(10,(size x number-of-shards))` to allow for more a accurate count of the
+top cells in the final result.

server/src/main/java/org/elasticsearch/search/aggregations/bucket/geogrid/InternalGeoGridBucket.java

@@ -51,7 +51,7 @@ public void writeTo(StreamOutput out) throws IOException {
         aggregations.writeTo(out);
     }
 
-    protected long hashAsLong() {
+    public long hashAsLong() {
         return hashAsLong;
     }
 

server/src/main/java/org/elasticsearch/search/aggregations/bucket/geogrid/ParsedGeoGrid.java

@@ -34,7 +34,7 @@ public static ObjectParser<ParsedGeoGrid, Void> createParser(
         return parser;
     }
 
-    protected void setName(String name) {
+    public void setName(String name) {
         super.setName(name);
     }
 }

test/framework/src/main/java/org/elasticsearch/search/aggregations/bucket/geogrid/GeoGridTestCase.java

@@ -55,16 +55,22 @@ protected int maxNumberOfBuckets() {
     @Override
     protected T createTestInstance(String name, Map<String, Object> metadata, InternalAggregations aggregations) {
         final int precision = randomPrecision();
-        int size = randomNumberOfBuckets();
-        List<InternalGeoGridBucket> buckets = new ArrayList<>(size);
+        final int size = randomNumberOfBuckets();
+        final List<InternalGeoGridBucket> buckets = new ArrayList<>(size);
+        final List<Long> seen = new ArrayList<>(size);
+        int finalSize = 0;
         for (int i = 0; i < size; i++) {
             double latitude = randomDoubleBetween(-90.0, 90.0, false);
             double longitude = randomDoubleBetween(-180.0, 180.0, false);
 
             long hashAsLong = longEncode(longitude, latitude, precision);
-            buckets.add(createInternalGeoGridBucket(hashAsLong, randomInt(IndexWriter.MAX_DOCS), aggregations));
+            if (seen.contains(hashAsLong) == false) { // make sure we don't add twice the same bucket
+                buckets.add(createInternalGeoGridBucket(hashAsLong, randomInt(IndexWriter.MAX_DOCS), aggregations));
+                seen.add(hashAsLong);
+                finalSize++;
+            }
         }
-        return createInternalGeoGrid(name, size, buckets, metadata);
+        return createInternalGeoGrid(name, finalSize, buckets, metadata);
     }
 
     @Override

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/spatial/action/SpatialStatsAction.java

@@ -39,7 +39,8 @@ private SpatialStatsAction() {
      * Items to track. Serialized by ordinals. Append only, don't remove or change order of items in this list.
      */
     public enum Item {
-        GEOLINE
+        GEOLINE,
+        GEOHEX
     }
 
     public static class Request extends BaseNodesRequest<Request> implements ToXContentObject {

x-pack/plugin/spatial/build.gradle

@@ -14,6 +14,7 @@ dependencies {
   compileOnly project(path: ':modules:legacy-geo')
   compileOnly project(':modules:lang-painless:spi')
   compileOnly project(path: xpackModule('core'))
+  api project(":libs:elasticsearch-h3")
   testImplementation(testArtifact(project(xpackModule('core'))))
   testImplementation project(path: xpackModule('vector-tile'))
 }