Use provider built-in result count to reuse query if possible

Hibernate introduce `SelectionQuery::getResultCount` since 6.5.0, It may be JPA Query method in the future.

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/AbstractJpaQuery.java

@@ -62,6 +62,7 @@
  * @author Сергей Цыпанов
  * @author Wonchul Heo
  * @author Julia Lee
+ * @author Yanming Zhou
  */
 public abstract class AbstractJpaQuery implements RepositoryQuery {
 
@@ -99,7 +100,7 @@ public AbstractJpaQuery(JpaQueryMethod method, EntityManager em) {
 			} else if (method.isSliceQuery()) {
 				return new SlicedExecution();
 			} else if (method.isPageQuery()) {
-				return new PagedExecution();
+				return new PagedExecution(em);
 			} else if (method.isModifyingQuery()) {
 				return null;
 			} else {

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java

@@ -24,7 +24,9 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
+import java.util.function.LongSupplier;
 
+import org.hibernate.query.SelectionQuery;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.support.ConfigurableConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
@@ -57,6 +59,7 @@
  * @author Jens Schauder
  * @author Gabriel Basilio
  * @author Greg Turnquist
+ * @author Yanming Zhou
  */
 public abstract class JpaQueryExecution {
 
@@ -195,14 +198,30 @@ protected Object doExecute(AbstractJpaQuery query, JpaParametersParameterAccesso
 	 */
 	static class PagedExecution extends JpaQueryExecution {
 
+		private final EntityManager em;
+
+		public PagedExecution(EntityManager em) {
+
+			Assert.notNull(em, "The EntityManager must not be null");
+			this.em = em;
+		}
+
 		@Override
 		@SuppressWarnings("unchecked")
 		protected Object doExecute(AbstractJpaQuery repositoryQuery, JpaParametersParameterAccessor accessor) {
 
 			Query query = repositoryQuery.createQuery(accessor);
 
-			return PageableExecutionUtils.getPage(query.getResultList(), accessor.getPageable(),
-					() -> count(repositoryQuery, accessor));
+			LongSupplier count = () -> {
+				boolean userDefinedCountQuery = (repositoryQuery instanceof AbstractStringBasedJpaQuery);
+				if (!userDefinedCountQuery && PersistenceProvider.fromEntityManager(em) == PersistenceProvider.HIBERNATE) {
+					// Hibernate introduce SelectionQuery::getResultCount since 6.5.0
+					return ((SelectionQuery<?>) query).getResultCount();
+				}
+				return count(repositoryQuery, accessor);
+			};
+
+			return PageableExecutionUtils.getPage(query.getResultList(), accessor.getPageable(), count);
 		}
 
 		private long count(AbstractJpaQuery repositoryQuery, JpaParametersParameterAccessor accessor) {

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/query/JpaQueryExecutionUnitTests.java

@@ -76,6 +76,7 @@ public static void sampleMethod(Pageable pageable) {}
 	@BeforeEach
 	void setUp() {
 
+		when(em.getDelegate()).thenReturn(em); // for PersistenceProvider.fromEntityManager(em)
 		when(query.executeUpdate()).thenReturn(0);
 		when(jpaQuery.createQuery(Mockito.any(JpaParametersParameterAccessor.class))).thenReturn(query);
 		when(jpaQuery.getQueryMethod()).thenReturn(method);
@@ -183,7 +184,7 @@ void pagedExecutionRetrievesObjectsForPageableOutOfRange() throws Exception {
 		when(jpaQuery.createQuery(Mockito.any())).thenReturn(query);
 		when(countQuery.getResultList()).thenReturn(Arrays.asList(20L));
 
-		PagedExecution execution = new PagedExecution();
+		PagedExecution execution = new PagedExecution(em);
 		execution.doExecute(jpaQuery,
 				new JpaParametersParameterAccessor(parameters, new Object[] { PageRequest.of(2, 10) }));
 
@@ -199,7 +200,7 @@ void pagedExecutionShouldNotGenerateCountQueryIfQueryReportedNoResults() throws
 		when(jpaQuery.createQuery(Mockito.any())).thenReturn(query);
 		when(query.getResultList()).thenReturn(Arrays.asList(0L));
 
-		PagedExecution execution = new PagedExecution();
+		PagedExecution execution = new PagedExecution(em);
 		execution.doExecute(jpaQuery,
 				new JpaParametersParameterAccessor(parameters, new Object[] { PageRequest.of(0, 10) }));
 
@@ -215,7 +216,7 @@ void pagedExecutionShouldUseCountFromResultIfOffsetIsZeroAndResultsWithinPageSiz
 		when(jpaQuery.createQuery(Mockito.any())).thenReturn(query);
 		when(query.getResultList()).thenReturn(Arrays.asList(new Object(), new Object(), new Object(), new Object()));
 
-		PagedExecution execution = new PagedExecution();
+		PagedExecution execution = new PagedExecution(em);
 		execution.doExecute(jpaQuery,
 				new JpaParametersParameterAccessor(parameters, new Object[] { PageRequest.of(0, 10) }));
 
@@ -230,7 +231,7 @@ void pagedExecutionShouldUseCountFromResultWithOffsetAndResultsWithinPageSize()
 		when(jpaQuery.createQuery(Mockito.any())).thenReturn(query);
 		when(query.getResultList()).thenReturn(Arrays.asList(new Object(), new Object(), new Object(), new Object()));
 
-		PagedExecution execution = new PagedExecution();
+		PagedExecution execution = new PagedExecution(em);
 		execution.doExecute(jpaQuery,
 				new JpaParametersParameterAccessor(parameters, new Object[] { PageRequest.of(5, 10) }));
 
@@ -247,7 +248,7 @@ void pagedExecutionShouldUseRequestCountFromResultWithOffsetAndResultsHitLowerPa
 		when(jpaQuery.createCountQuery(Mockito.any())).thenReturn(query);
 		when(countQuery.getResultList()).thenReturn(Arrays.asList(20L));
 
-		PagedExecution execution = new PagedExecution();
+		PagedExecution execution = new PagedExecution(em);
 		execution.doExecute(jpaQuery,
 				new JpaParametersParameterAccessor(parameters, new Object[] { PageRequest.of(4, 4) }));
 
@@ -264,7 +265,7 @@ void pagedExecutionShouldUseRequestCountFromResultWithOffsetAndResultsHitUpperPa
 		when(jpaQuery.createCountQuery(Mockito.any())).thenReturn(query);
 		when(countQuery.getResultList()).thenReturn(Arrays.asList(20L));
 
-		PagedExecution execution = new PagedExecution();
+		PagedExecution execution = new PagedExecution(em);
 		execution.doExecute(jpaQuery,
 				new JpaParametersParameterAccessor(parameters, new Object[] { PageRequest.of(4, 4) }));