DATAMONGO-445 - Allow to skip unnecessary elements in NearQuery.

Added support for skipping elements for NearQuery in MongoTemplate. As mongodb currently (2.4.4) doesn't support he skipping of elements in geoNear-Queries we skip the unnecessary elements ourselves. We use the limit & skip information from the given query or an explicitly passed Pageable.

Original pull request: #64.

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

@@ -566,9 +566,27 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 				mongoConverter, entityClass), near.getMetric());
 		List<GeoResult<T>> result = new ArrayList<GeoResult<T>>(results.size());
 
+		int index = 0;
+		int elementsToSkip = near.getSkip() != null ? near.getSkip() : 0;
+
 		for (Object element : results) {
+
+			/*
+			 * As MongoDB currently (2.4.4) doesn't support the skipping of elements in near queries
+			 * we skip the elements ourselves to avoid at least the document 2 object mapping overhead.
+			 * 
+			 * @see https://jira.mongodb.org/browse/SERVER-3925
+			 */
+			if (index >= elementsToSkip) {
 				result.add(callback.doWith((DBObject) element));
 			}
+			index++;
+		}
+
+		if (elementsToSkip > 0) {
+			// as we skipped some elements we have to calculate the averageDistance ourselves:
+			return new GeoResults<T>(result, near.getMetric());
+		}
 
 		DBObject stats = (DBObject) commandResult.get("stats");
 		double averageDistance = stats == null ? 0 : (Double) stats.get("avgDistance");

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

@@ -131,7 +131,7 @@ public class GeoResults<T> implements Iterable<GeoResult<T>> {
 	private static Distance calculateAverageDistance(List<? extends GeoResult<?>> results, Metric metric) {
 
 		if (results.isEmpty()) {
-			return new Distance(0, null);
+			return new Distance(0, metric);
 		}
 
 		double averageDistance = 0;

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

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.mongodb.core.query;
 
+import org.springframework.data.domain.Pageable;
 import org.springframework.data.mongodb.core.geo.CustomMetric;
 import org.springframework.data.mongodb.core.geo.Distance;
 import org.springframework.data.mongodb.core.geo.Metric;
@@ -29,6 +30,7 @@ import com.mongodb.DBObject;
  * Builder class to build near-queries.
  * 
  * @author Oliver Gierke
+ * @author Thomas Darimont
  */
 public class NearQuery {
 
@@ -38,6 +40,7 @@ public class NearQuery {
 	private Metric metric;
 	private boolean spherical;
 	private Integer num;
+	private Integer skip;
 
 	/**
 	 * Creates a new {@link NearQuery}.
@@ -116,7 +119,7 @@ public class NearQuery {
 	}
 
 	/**
-	 * Configures the number of results to return.
+	 * Configures the maximum number of results to return.
 	 * 
 	 * @param num
 	 * @return
@@ -126,6 +129,29 @@ public class NearQuery {
 		return this;
 	}
 
+	/**
+	 * Configures the number of results to skip.
+	 * 
+	 * @param skip
+	 * @return
+	 */
+	public NearQuery skip(int skip) {
+		this.skip = skip;
+		return this;
+	}
+
+	/**
+	 * Configures the {@link Pageable} to use.
+	 * 
+	 * @param pageable
+	 * @return
+	 */
+	public NearQuery with(Pageable pageable) {
+		this.num = pageable.getOffset() + pageable.getPageSize();
+		this.skip = pageable.getOffset();
+		return this;
+	}
+
 	/**
 	 * Sets the max distance results shall have from the configured origin. If a {@link Metric} was set before the given
 	 * value will be interpreted as being a value in that metric. E.g.
@@ -290,9 +316,18 @@ public class NearQuery {
 	 */
 	public NearQuery query(Query query) {
 		this.query = query;
+		this.skip = query.getSkip();
+		this.num = query.getLimit();
 		return this;
 	}
 
+	/**
+	 * @return the number of elements to skip.
+	 */
+	public Integer getSkip() {
+		return skip;
+	}
+
 	/**
 	 * Returns the {@link DBObject} built by the {@link NearQuery}.
 	 * 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AbstractMongoQuery.java

@@ -38,6 +38,7 @@ import org.springframework.util.Assert;
  * Base class for {@link RepositoryQuery} implementations for Mongo.
  * 
  * @author Oliver Gierke
+ * @author Thomas Darimont
  */
 public abstract class AbstractMongoQuery implements RepositoryQuery {
 
@@ -287,6 +288,11 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 				nearQuery.maxDistance(maxDistance).in(maxDistance.getMetric());
 			}
 
+			Pageable pageable = accessor.getPageable();
+			if (pageable != null) {
+				nearQuery.with(pageable);
+			}
+
 			MongoEntityMetadata<?> metadata = method.getEntityInformation();
 			return (GeoResults<Object>) operations.geoNear(nearQuery, metadata.getJavaType(), metadata.getCollectionName());
 		}

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

@@ -19,14 +19,18 @@ import static org.hamcrest.CoreMatchers.*;
 import static org.junit.Assert.*;
 
 import org.junit.Test;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
 import org.springframework.data.mongodb.core.geo.Distance;
 import org.springframework.data.mongodb.core.geo.Metric;
 import org.springframework.data.mongodb.core.geo.Metrics;
+import org.springframework.data.mongodb.core.geo.Point;
 
 /**
  * Unit tests for {@link NearQuery}.
  * 
  * @author Oliver Gierke
+ * @author Thomas Darimont
  */
 public class NearQueryUnitTests {
 
@@ -75,4 +79,48 @@ public class NearQueryUnitTests {
 		query = query.maxDistance(new Distance(200, Metrics.KILOMETERS));
 		assertThat(query.getMetric(), is((Metric) Metrics.MILES));
 	}
+
+	/**
+	 * @see DATAMONGO-445
+	 */
+	@Test
+	public void shouldTakeSkipAndLimitSettingsFromGivenPageable() {
+
+		Pageable pageable = new PageRequest(3, 5);
+		NearQuery query = NearQuery.near(new Point(1, 1)).with(pageable);
+
+		assertThat(query.getSkip(), is(pageable.getPageNumber() * pageable.getPageSize()));
+		assertThat((Integer) query.toDBObject().get("num"), is((pageable.getPageNumber() + 1) * pageable.getPageSize()));
+	}
+
+	/**
+	 * @see DATAMONGO-445
+	 */
+	@Test
+	public void shouldTakeSkipAndLimitSettingsFromGivenQuery() {
+
+		int limit = 10;
+		int skip = 5;
+		NearQuery query = NearQuery.near(new Point(1, 1)).query(
+				Query.query(Criteria.where("foo").is("bar")).limit(limit).skip(skip));
+
+		assertThat(query.getSkip(), is(skip));
+		assertThat((Integer) query.toDBObject().get("num"), is(limit));
+	}
+
+	/**
+	 * @see DATAMONGO-445
+	 */
+	@Test
+	public void shouldTakeSkipAndLimitSettingsFromPageableEvenIfItWasSpecifiedOnQuery() {
+
+		int limit = 10;
+		int skip = 5;
+		Pageable pageable = new PageRequest(3, 5);
+		NearQuery query = NearQuery.near(new Point(1, 1))
+				.query(Query.query(Criteria.where("foo").is("bar")).limit(limit).skip(skip)).with(pageable);
+
+		assertThat(query.getSkip(), is(pageable.getPageNumber() * pageable.getPageSize()));
+		assertThat((Integer) query.toDBObject().get("num"), is((pageable.getPageNumber() + 1) * pageable.getPageSize()));
+	}
 }

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/AbstractPersonRepositoryIntegrationTests.java

@@ -590,4 +590,94 @@ public abstract class AbstractPersonRepositoryIntegrationTests {
 		assertThat(result, hasSize(2));
 		assertThat(result, hasItems(dave, oliver));
 	}
+
+	/**
+	 * @see DATAMONGO-445
+	 */
+	@Test
+	public void executesGeoPageQueryForWithPageRequestForPageInBetween() {
+
+		Point farAway = new Point(-73.9, 40.7);
+		Point here = new Point(-73.99, 40.73);
+
+		dave.setLocation(farAway);
+		oliver.setLocation(here);
+		carter.setLocation(here);
+		boyd.setLocation(here);
+		leroi.setLocation(here);
+
+		repository.save(Arrays.asList(dave, oliver, carter, boyd, leroi));
+
+		GeoPage<Person> results = repository.findByLocationNear(new Point(-73.99, 40.73), new Distance(2000,
+				Metrics.KILOMETERS), new PageRequest(1, 2));
+
+		assertThat(results.getContent().isEmpty(), is(false));
+		assertThat(results.getNumberOfElements(), is(2));
+		assertThat(results.isFirstPage(), is(false));
+		assertThat(results.isLastPage(), is(false));
+		assertThat(results.getAverageDistance().getMetric(), is((Metric) Metrics.KILOMETERS));
+		assertThat(results.getAverageDistance().getNormalizedValue(), is(0.0));
+	}
+
+	/**
+	 * @see DATAMONGO-445
+	 */
+	@Test
+	public void executesGeoPageQueryForWithPageRequestForPageAtTheEnd() {
+
+		Point point = new Point(-73.99171, 40.738868);
+
+		dave.setLocation(point);
+		oliver.setLocation(point);
+		carter.setLocation(point);
+
+		repository.save(Arrays.asList(dave, oliver, carter));
+
+		GeoPage<Person> results = repository.findByLocationNear(new Point(-73.99, 40.73), new Distance(2000,
+				Metrics.KILOMETERS), new PageRequest(1, 2));
+		assertThat(results.getContent().isEmpty(), is(false));
+		assertThat(results.getNumberOfElements(), is(1));
+		assertThat(results.isFirstPage(), is(false));
+		assertThat(results.isLastPage(), is(true));
+		assertThat(results.getAverageDistance().getMetric(), is((Metric) Metrics.KILOMETERS));
+	}
+
+	/**
+	 * @see DATAMONGO-445
+	 */
+	@Test
+	public void executesGeoPageQueryForWithPageRequestForJustOneElement() {
+
+		Point point = new Point(-73.99171, 40.738868);
+		dave.setLocation(point);
+		repository.save(dave);
+
+		GeoPage<Person> results = repository.findByLocationNear(new Point(-73.99, 40.73), new Distance(2000,
+				Metrics.KILOMETERS), new PageRequest(0, 2));
+
+		assertThat(results.getContent().isEmpty(), is(false));
+		assertThat(results.getNumberOfElements(), is(1));
+		assertThat(results.isFirstPage(), is(true));
+		assertThat(results.isLastPage(), is(true));
+		assertThat(results.getAverageDistance().getMetric(), is((Metric) Metrics.KILOMETERS));
+	}
+
+	/**
+	 * @see DATAMONGO-445
+	 */
+	@Test
+	public void executesGeoPageQueryForWithPageRequestForJustOneElementEmptyPage() {
+
+		dave.setLocation(new Point(-73.99171, 40.738868));
+		repository.save(dave);
+
+		GeoPage<Person> results = repository.findByLocationNear(new Point(-73.99, 40.73), new Distance(2000,
+				Metrics.KILOMETERS), new PageRequest(1, 2));
+
+		assertThat(results.getContent().isEmpty(), is(true));
+		assertThat(results.getNumberOfElements(), is(0));
+		assertThat(results.isFirstPage(), is(false));
+		assertThat(results.isLastPage(), is(true));
+		assertThat(results.getAverageDistance().getMetric(), is((Metric) Metrics.KILOMETERS));
+	}
 }