Fix rewrite near & nearSphere count queries using geoJson to geoWithin.

$near and $nearSphere queries are not supported via countDocuments and the used aggregation match stage and need to be rewritten to $geoWithin. The existing logic did not cover usage of geoJson types, which is fixed now. In case of nearSphere it is also required to convert the $maxDistance argument (given in meters for geoJson) to radians which is used by $geoWithin $centerSphere.

Closes #4004
Original pull request: #4006.
Related to #2925

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/CountQuery.java

@@ -23,8 +23,8 @@ import java.util.List;
 import java.util.Map;
 
 import org.bson.Document;
-
 import org.springframework.data.geo.Point;
+import org.springframework.data.mongodb.core.query.MetricConversion;
 import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
@@ -162,7 +162,8 @@ class CountQuery {
 		boolean spheric = source.containsKey("$nearSphere");
 		Object $near = spheric ? source.get("$nearSphere") : source.get("$near");
 
-		Number maxDistance = source.containsKey("$maxDistance") ? (Number) source.get("$maxDistance") : Double.MAX_VALUE;
+		Number maxDistance = getMaxDistance(source, $near, spheric);
+
 		List<Object> $centerMax = Arrays.asList(toCenterCoordinates($near), maxDistance);
 		Document $geoWithinMax = new Document("$geoWithin",
 				new Document(spheric ? "$centerSphere" : "$center", $centerMax));
@@ -197,6 +198,24 @@ class CountQuery {
 		return new Document("$and", criteria);
 	}
 
+	private static Number getMaxDistance(Document source, Object $near, boolean spheric) {
+
+		Number maxDistance = Double.MAX_VALUE;
+		if(source.containsKey("$maxDistance")) { // legacy coordinate pair
+			maxDistance = (Number) source.get("$maxDistance");
+		} else if ($near instanceof Document) {
+			Document nearDoc = (Document)$near;
+			if(nearDoc.containsKey("$maxDistance")) {
+				maxDistance = (Number) nearDoc.get("$maxDistance");
+				// geojson is in Meters but we need radians x/(6378.1*1000)
+				if(spheric && nearDoc.containsKey("$geometry")) {
+					maxDistance = MetricConversion.metersToRadians(maxDistance.doubleValue());
+				}
+			}
+		}
+		return maxDistance;
+	}
+
 	private static boolean containsNear(Document source) {
 		return source.containsKey("$near") || source.containsKey("$nearSphere");
 	}
@@ -220,10 +239,16 @@ class CountQuery {
 			return Arrays.asList(((Point) value).getX(), ((Point) value).getY());
 		}
 
-		if (value instanceof Document && ((Document) value).containsKey("x")) {
-
-			Document point = (Document) value;
-			return Arrays.asList(point.get("x"), point.get("y"));
+		if (value instanceof Document ) {
+			Document document = (Document) value;
+			if(document.containsKey("x")) {
+				Document point = document;
+				return Arrays.asList(point.get("x"), point.get("y"));
+			}
+			else if (document.containsKey("$geometry")) {
+				Document geoJsonPoint = document.get("$geometry", Document.class);
+				return geoJsonPoint.get("coordinates");
+			}
 		}
 
 		return value;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/query/MetricConversion.java

@@ -17,6 +17,7 @@
 package org.springframework.data.mongodb.core.query;
 
 import java.math.BigDecimal;
+import java.math.MathContext;
 import java.math.RoundingMode;
 
 import org.springframework.data.geo.Distance;
@@ -27,6 +28,7 @@ import org.springframework.data.geo.Metrics;
  * {@link Metric} and {@link Distance} conversions using the metric system.
  *
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 2.2
  */
 public class MetricConversion {
@@ -61,6 +63,28 @@ public class MetricConversion {
 				.doubleValue();
 	}
 
+	/**
+	 * Return {@code distance} in radians (on an earth like sphere).
+	 *
+	 * @param distance must not be {@literal null}.
+	 * @return distance in rads.
+	 * @since 3.4
+	 */
+	public static double toRadians(Distance distance) {
+		return metersToRadians(getDistanceInMeters(distance));
+	}
+
+	/**
+	 * Return {@code distance} in radians (on an earth like sphere).
+	 *
+	 * @param meters
+	 * @return distance in rads.
+	 * @since 3.4
+	 */
+	public static double metersToRadians(double meters) {
+		return BigDecimal.valueOf(meters).divide(METERS_MULTIPLIER, MathContext.DECIMAL64).doubleValue();
+	}
+
 	/**
 	 * Return {@code metric} to meters multiplier.
 	 *

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/CountQueryUnitTests.java

@@ -29,6 +29,7 @@ import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
 import org.springframework.data.mongodb.core.convert.NoOpDbRefResolver;
 import org.springframework.data.mongodb.core.convert.QueryMapper;
+import org.springframework.data.mongodb.core.geo.GeoJsonPoint;
 import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.query.Criteria;
@@ -155,6 +156,39 @@ class CountQueryUnitTests {
 				"{\"$or\" : [ { \"name\": \"food\" }, {\"location\": {\"$geoWithin\": {\"$center\": [[-73.99171, 40.738868], 10.0]}}} ]}"));
 	}
 
+	@Test // GH-4004
+	void nearToGeoWithinWithMaxDistanceUsingGeoJsonSource() {
+
+		Query source = query(new Criteria().orOperator(where("name").is("food"),
+				where("location").near(new GeoJsonPoint(-73.99171, 40.738868)).maxDistance(10)));
+
+		org.bson.Document target = postProcessQueryForCount(source);
+		assertThat(target).isEqualTo(org.bson.Document.parse(
+				"{\"$or\" : [ { \"name\": \"food\" }, {\"location\": {\"$geoWithin\": {\"$center\": [[-73.99171, 40.738868], 10.0]}}} ]}"));
+	}
+
+	@Test // GH-4004
+	void nearSphereToGeoWithinWithoutMaxDistanceUsingGeoJsonSource() {
+
+		Query source = query(new Criteria().orOperator(where("name").is("food"),
+				where("location").nearSphere(new GeoJsonPoint(-73.99171, 40.738868))));
+
+		org.bson.Document target = postProcessQueryForCount(source);
+		assertThat(target).isEqualTo(org.bson.Document.parse(
+				"{\"$or\" : [ { \"name\": \"food\" }, {\"location\": {\"$geoWithin\": {\"$centerSphere\": [[-73.99171, 40.738868], 1.7976931348623157E308]}}} ]}"));
+	}
+
+	@Test // GH-4004
+	void nearSphereToGeoWithinWithMaxDistanceUsingGeoJsonSource() {
+
+		Query source = query(new Criteria().orOperator(where("name").is("food"), where("location")
+				.nearSphere(new GeoJsonPoint(-73.99171, 40.738868)).maxDistance/*in meters for geojson*/(10d)));
+
+		org.bson.Document target = postProcessQueryForCount(source);
+		assertThat(target).isEqualTo(org.bson.Document.parse(
+				"{\"$or\" : [ { \"name\": \"food\" }, {\"location\": {\"$geoWithin\": {\"$centerSphere\": [[-73.99171, 40.738868], 1.567855942887398E-6]}}} ]}"));
+	}
+
 	private org.bson.Document postProcessQueryForCount(Query source) {
 
 		org.bson.Document intermediate = mapper.getMappedObject(source.getQueryObject(), (MongoPersistentEntity<?>) null);

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/query/MetricConversionUnitTests.java

@@ -65,4 +65,18 @@ public class MetricConversionUnitTests {
 		assertThat(multiplier).isCloseTo(0.00062137, offset(0.000000001));
 	}
 
+	@Test // GH-4004
+	void shouldConvertMetersToRadians/* on an earth like sphere with r=6378.137km */() {
+		assertThat(MetricConversion.metersToRadians(1000)).isCloseTo(0.000156785594d, offset(0.000000001));
+	}
+
+	@Test // GH-4004
+	void shouldConvertKilometersToRadians/* on an earth like sphere with r=6378.137km */() {
+		assertThat(MetricConversion.toRadians(new Distance(1, Metrics.KILOMETERS))).isCloseTo(0.000156785594d, offset(0.000000001));
+	}
+
+	@Test // GH-4004
+	void shouldConvertMilesToRadians/* on an earth like sphere with r=6378.137km */() {
+		assertThat(MetricConversion.toRadians(new Distance(1, Metrics.MILES))).isCloseTo(0.000252321328d, offset(0.000000001));
+	}
 }