Check leniently for built-in exists query results.

We now check whether the exists-count is greater than zero instead of checking for 1. This enables uses with partial primary keys, although non-unique primary keys will generally fail when using by-id lookups.

Closes #4227

Author: mp911de

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/support/ExistsUtil.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2026-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jpa.repository.support;
+
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Utility to determine whether a query result exists.
+ *
+ * @author Mark Paluch
+ * @since 4.0.5
+ */
+class ExistsUtil {
+
+	/**
+	 * Determine whether the given count is greater than zero.
+	 */
+	public static boolean exists(long count) {
+		return count > 0;
+	}
+
+	/**
+	 * Determine whether the given count is greater than zero.
+	 */
+	public static boolean exists(@Nullable Long singleResult) {
+		return singleResult != null && exists(singleResult.longValue());
+	}
+
+}

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java

@@ -385,7 +385,7 @@ public boolean existsById(ID id) {
 
 		if (!entityInformation.hasCompositeId()) {
 			query.setParameter(idAttributeNames.iterator().next(), id);
-			return query.getSingleResult() == 1L;
+			return ExistsUtil.exists(query.getSingleResult());
 		}
 
 		for (String idAttributeName : idAttributeNames) {
@@ -404,7 +404,7 @@ public boolean existsById(ID id) {
 			query.setParameter(idAttributeName, idAttributeValue);
 		}
 
-		return query.getSingleResult() == 1L;
+		return ExistsUtil.exists(query.getSingleResult());
 	}
 
 	@Override
@@ -497,7 +497,7 @@ public boolean exists(Specification<T> spec) {
 		applySpecificationToCriteria(spec, getDomainClass(), cq);
 
 		TypedQuery<Integer> query = applyRepositoryMethodMetadata(this.entityManager.createQuery(cq));
-		return query.setMaxResults(1).getResultList().size() == 1;
+		return ExistsUtil.exists(query.setMaxResults(1).getResultList().size());
 	}
 
 	@Override
@@ -601,7 +601,7 @@ public <S extends T> boolean exists(Example<S> example) {
 		applySpecificationToCriteria(spec, example.getProbeType(), cq);
 
 		TypedQuery<Integer> query = applyRepositoryMethodMetadata(this.entityManager.createQuery(cq));
-		return query.setMaxResults(1).getResultList().size() == 1;
+		return ExistsUtil.exists(query.setMaxResults(1).getResultList().size());
 	}
 
 	@Override

spring-data-jpa/src/test/java/org/springframework/data/jpa/domain/sample/SampleEntity.java

@@ -17,11 +17,13 @@
 
 import jakarta.persistence.EmbeddedId;
 import jakarta.persistence.Entity;
+import jakarta.persistence.Table;
 
 /**
  * @author Oliver Gierke
  */
 @Entity
+@Table(name = "sample_entity")
 public class SampleEntity {
 
 	@EmbeddedId

spring-data-jpa/src/test/java/org/springframework/data/jpa/domain/sample/SampleEntityPartialKey.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2026-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jpa.domain.sample;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+
+import org.hibernate.annotations.Immutable;
+import org.hibernate.annotations.Subselect;
+
+/**
+ * @author Mark Paluch
+ */
+@Entity
+@Immutable
+@Subselect("""
+		    select first
+		    from sample_entity
+		""")
+public class SampleEntityPartialKey {
+
+	@Id private String first;
+
+	public SampleEntityPartialKey() {}
+
+	public SampleEntityPartialKey(String first) {
+		this.first = first;
+	}
+
+	public String getFirst() {
+		return first;
+	}
+
+	public void setFirst(String first) {
+		this.first = first;
+	}
+}

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/support/EclipseLinkJpaRepositoryTests.java

@@ -77,6 +77,12 @@ void deleteAllInBatch() {
 		assertThat(repository.count()).isZero();
 	}
 
+	@Test
+	@Disabled("We cannot currently setup a read-only entity to simulate a partial key on top of an entity with a composite key")
+	void shouldReportExistsForPartialKeyEntity() {
+
+	}
+
 	@Override
 	@Disabled("https://bugs.eclipse.org/bugs/show_bug.cgi?id=349477")
 	void deleteAllByIdInBatch() {

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/support/JpaRepositoryTests.java

@@ -27,10 +27,13 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.data.domain.Example;
 import org.springframework.data.jpa.domain.sample.PersistableWithIdClass;
 import org.springframework.data.jpa.domain.sample.PersistableWithIdClassPK;
 import org.springframework.data.jpa.domain.sample.SampleEntity;
 import org.springframework.data.jpa.domain.sample.SampleEntityPK;
+import org.springframework.data.jpa.domain.sample.SampleEntityPartialKey;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.repository.CrudRepository;
 import org.springframework.test.context.ContextConfiguration;
@@ -45,6 +48,7 @@
  * @author Jens Schauder
  * @author Greg Turnquist
  * @author Krzysztof Krason
+ * @author Mark Paluch
  */
 @ExtendWith(SpringExtension.class)
 @ContextConfiguration("classpath:hibernate-infrastructure.xml")
@@ -55,11 +59,14 @@ class JpaRepositoryTests {
 
 	private JpaRepository<SampleEntity, SampleEntityPK> repository;
 	private CrudRepository<PersistableWithIdClass, PersistableWithIdClassPK> idClassRepository;
+	private SamplePartialKeyEntityRepository partialKey;
 
 	@BeforeEach
 	void setUp() {
-		repository = new JpaRepositoryFactory(em).getRepository(SampleEntityRepository.class);
-		idClassRepository = new JpaRepositoryFactory(em).getRepository(SampleWithIdClassRepository.class);
+		JpaRepositoryFactory factory = new JpaRepositoryFactory(em);
+		repository = factory.getRepository(SampleEntityRepository.class);
+		idClassRepository = factory.getRepository(SampleWithIdClassRepository.class);
+		partialKey = factory.getRepository(SamplePartialKeyEntityRepository.class);
 	}
 
 	@Test
@@ -78,6 +85,19 @@ void testCrudOperationsForCompoundKeyEntity() {
 		assertThat(repository.count()).isZero();
 	}
 
+	@Test
+	void shouldReportExistsForPartialKeyEntity() {
+
+		repository.saveAndFlush(new SampleEntity("foo", "bar"));
+		repository.saveAndFlush(new SampleEntity("foo", "baz"));
+		repository.saveAndFlush(new SampleEntity("foo", "foo"));
+		repository.flush();
+
+		assertThat(partialKey.existsById("foo")).isTrue();
+		assertThat(partialKey.exists(Example.of(new SampleEntityPartialKey("foo")))).isTrue();
+		assertThat(partialKey.existsByFirst("foo")).isTrue();
+	}
+
 	@Test // DATAJPA-50
 	void executesCrudOperationsForEntityWithIdClass() {
 
@@ -164,6 +184,12 @@ private interface SampleEntityRepository extends JpaRepository<SampleEntity, Sam
 
 	}
 
+	private interface SamplePartialKeyEntityRepository extends JpaRepository<SampleEntityPartialKey, String> {
+
+		boolean existsByFirst(String first);
+
+	}
+
 	private interface SampleWithIdClassRepository
 			extends CrudRepository<PersistableWithIdClass, PersistableWithIdClassPK> {
 

spring-data-jpa/src/test/resources/META-INF/persistence.xml

@@ -54,6 +54,7 @@
 		<class>org.springframework.data.jpa.domain.sample.SampleWithIdClass</class>
 		<class>org.springframework.data.jpa.domain.sample.SampleWithPrimitiveId</class>
 		<class>org.springframework.data.jpa.domain.sample.SampleWithTimestampVersion</class>
+		<class>org.springframework.data.jpa.domain.sample.SampleEntityPartialKey</class>
 		<class>org.springframework.data.jpa.domain.sample.Site</class>
 		<class>org.springframework.data.jpa.domain.sample.SpecialUser</class>
 		<class>org.springframework.data.jpa.domain.sample.User</class>