DATAMONGO-1860 - Retrieve result count via QuerydslMongoPredicateExecutor only for paging.

We now use AbstractMongodbQuery.fetch() instead of AbstractMongodbQuery.fetchResults() to execute MongoDB queries. fetchResults() executes a find(…) and a count(…) query. Retrieving the record count is an expensive operation in MongoDB and the count is not always required. For regular find(…) method, the count is ignored, for paging the count(…) is only required in certain result/request scenarios.

Original Pull Request: #529

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/QueryDslMongoRepository.java

@@ -35,6 +35,7 @@ import org.springframework.data.repository.support.PageableExecutionUtils;
 import org.springframework.data.repository.support.PageableExecutionUtils.TotalSupplier;
 import org.springframework.util.Assert;
 
+import com.querydsl.core.QueryResults;
 import com.querydsl.core.types.EntityPath;
 import com.querydsl.core.types.Expression;
 import com.querydsl.core.types.OrderSpecifier;
@@ -104,7 +105,7 @@ public class QueryDslMongoRepository<T, ID extends Serializable> extends SimpleM
 	 */
 	@Override
 	public List<T> findAll(Predicate predicate) {
-		return createQueryFor(predicate).fetchResults().getResults();
+		return createQueryFor(predicate).fetch();
 	}
 
 	/*
@@ -113,7 +114,7 @@ public class QueryDslMongoRepository<T, ID extends Serializable> extends SimpleM
 	 */
 	@Override
 	public List<T> findAll(Predicate predicate, OrderSpecifier<?>... orders) {
-		return createQueryFor(predicate).orderBy(orders).fetchResults().getResults();
+		return createQueryFor(predicate).orderBy(orders).fetch();
 	}
 
 	/*
@@ -122,7 +123,7 @@ public class QueryDslMongoRepository<T, ID extends Serializable> extends SimpleM
 	 */
 	@Override
 	public List<T> findAll(Predicate predicate, Sort sort) {
-		return applySorting(createQueryFor(predicate), sort).fetchResults().getResults();
+		return applySorting(createQueryFor(predicate), sort).fetch();
 	}
 
 	/*
@@ -131,7 +132,7 @@ public class QueryDslMongoRepository<T, ID extends Serializable> extends SimpleM
 	 */
 	@Override
 	public Iterable<T> findAll(OrderSpecifier<?>... orders) {
-		return createQuery().orderBy(orders).fetchResults().getResults();
+		return createQuery().orderBy(orders).fetch();
 	}
 
 	/*
@@ -143,11 +144,13 @@ public class QueryDslMongoRepository<T, ID extends Serializable> extends SimpleM
 
 		AbstractMongodbQuery<T, SpringDataMongodbQuery<T>> query = createQueryFor(predicate);
 
-		return PageableExecutionUtils.getPage(applyPagination(query, pageable).fetchResults().getResults(), pageable, new TotalSupplier() {
+		final QueryResults<T> results = applyPagination(query, pageable).fetchResults();
+
+		return PageableExecutionUtils.getPage(results.getResults(), pageable, new TotalSupplier() {
 
 			@Override
 			public long get() {
-				return createQueryFor(predicate).fetchCount();
+				return results.getTotal();
 			}
 		});
 	}
@@ -161,11 +164,13 @@ public class QueryDslMongoRepository<T, ID extends Serializable> extends SimpleM
 
 		AbstractMongodbQuery<T, SpringDataMongodbQuery<T>> query = createQuery();
 
-		return PageableExecutionUtils.getPage(applyPagination(query, pageable).fetchResults().getResults(), pageable, new TotalSupplier() {
+		final QueryResults<T> results = applyPagination(query, pageable).fetchResults();
+
+		return PageableExecutionUtils.getPage(results.getResults(), pageable, new TotalSupplier() {
 
 			@Override
 			public long get() {
-				return createQuery().fetchCount();
+				return results.getTotal();
 			}
 		});
 	}
@@ -176,7 +181,7 @@ public class QueryDslMongoRepository<T, ID extends Serializable> extends SimpleM
 	 */
 	@Override
 	public List<T> findAll(Sort sort) {
-		return applySorting(createQuery(), sort).fetchResults().getResults();
+		return applySorting(createQuery(), sort).fetch();
 	}
 
 	/*