具有加入和不同抛出错误的JPA标准

Question

我想同时运行count和distinct的标准。

我的代码如下：

final EntityManager entityManager = getEntityManagerFactory().createEntityManager();
final CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
final CriteriaQuery<Long> criteriaQuery = criteriaBuilder.createQuery(Long.class);
final Root<Manufacturer> root = criteriaQuery.from(Manufacturer.class);
criteriaQuery.select(criteriaBuilder.count(root));

final Join productJoin = root.join("products");
productJoin.join("nickNames");

criteriaQuery.distinct(true);

final TypedQuery<Long> countQuery = entityManager.createQuery(criteriaQuery);
System.out.println(countQuery.getSingleResult());

我的标准有问题吗？或者是一个OpenJPA错误？如果我删除了不同的查询执行没有问题。

根据上述标准，我收到以下异常消息：

Exception in thread "main" <openjpa-2.3.0-r422266:1540826 nonfatal user error> org.apache.openjpa.persistence.ArgumentException: Failed to execute query "null". Check the query syntax for correctness. See nested exception for details. at org.apache.openjpa.kernel.QueryImpl.execute(QueryImpl.java:872) at org.apache.openjpa.kernel.QueryImpl.execute(QueryImpl.java:794) at org.apache.openjpa.kernel.DelegatingQuery.execute(DelegatingQuery.java:542) at org.apache.openjpa.persistence.QueryImpl.execute(QueryImpl.java:275) at org.apache.openjpa.persistence.QueryImpl.getResultList(QueryImpl.java:291) at org.apache.openjpa.persistence.QueryImpl.getSingleResult(QueryImpl.java:319) at com.uaihebert.test.Main.main(Main.java:47) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134) Caused by: org.apache.openjpa.lib.jdbc.ReportingSQLException: unexpected token: FROM {SELECT DISTINCT FROM (SELECT DISTINCT t0.id AS t0_id FROM Manufacturer t0 INNER JOIN Manufacturer_Product t1 ON t0.id = t1.MANUFACTURER_ID INNER JOIN Product t2 ON t1.PRODUCTS_ID = t2.id INNER JOIN Product_NickName t3 ON t2.id = t3.PRODUCT_ID INNER JOIN NickName t4 ON t3.NICKNAMES_ID = t4.id)} [code=-5581, state=42581] at org.apache.openjpa.lib.jdbc.LoggingConnectionDecorator.wrap(LoggingConnectionDecorator.java:219) at org.apache.openjpa.lib.jdbc.LoggingConnectionDecorator.wrap(LoggingConnectionDecorator.java:199) at org.apache.openjpa.lib.jdbc.LoggingConnectionDecorator.access$000(LoggingConnectionDecorator.java:59) at org.apache.openjpa.lib.jdbc.LoggingConnectionDecorator$LoggingConnection.prepareStatement(LoggingConnectionDecorator.java:251) at org.apache.openjpa.lib.jdbc.DelegatingConnection.prepareStatement(DelegatingConnection.java:133) at org.apache.openjpa.lib.jdbc.ConfiguringConnectionDecorator$ConfiguringConnection.prepareStatement(ConfiguringConnectionDecorator.java:140) at org.apache.openjpa.lib.jdbc.DelegatingConnection.prepareStatement(DelegatingConnection.java:133) at org.apache.openjpa.jdbc.kernel.JDBCStoreManager$RefCountConnection.prepareStatement(JDBCStoreManager.java:1643) at org.apache.openjpa.lib.jdbc.DelegatingConnection.prepareStatement(DelegatingConnection.java:122) at org.apache.openjpa.jdbc.sql.SQLBuffer.prepareStatement(SQLBuffer.java:508) at org.apache.openjpa.jdbc.sql.SQLBuffer.prepareStatement(SQLBuffer.java:488) at org.apache.openjpa.jdbc.sql.SelectImpl.prepareStatement(SelectImpl.java:481) at org.apache.openjpa.jdbc.sql.SelectImpl.execute(SelectImpl.java:422) at org.apache.openjpa.jdbc.sql.SelectImpl.execute(SelectImpl.java:384) at org.apache.openjpa.jdbc.kernel.SelectResultObjectProvider.open(SelectResultObjectProvider.java:94) at org.apache.openjpa.kernel.QueryImpl$PackingResultObjectProvider.open(QueryImpl.java:2070) at org.apache.openjpa.kernel.QueryImpl.singleResult(QueryImpl.java:1320) at org.apache.openjpa.kernel.QueryImpl.toResult(QueryImpl.java:1242) at org.apache.openjpa.kernel.QueryImpl.execute(QueryImpl.java:1007) at org.apache.openjpa.kernel.QueryImpl.execute(QueryImpl.java:863) ... 11 more

Answer 1

尝试在代码中使用CriteriaBuilder#countDistinct()。

// ...

criteriaQuery.select(criteriaBuilder.countDistinct(root));

final Join productJoin = root.join("products");
productJoin.join("nickNames");

//criteriaQuery.distinct(true); -- commented u=out
// ...

在Hibernate 4.3.5下，您的查询效果很好，但可能是供应商特定的行为（不一定是OpenJPA's错误）。

我无法告诉count(..)然后distinct(true)与countDistinct(..)的区别，但从逻辑上讲，它与写DISTINCT(COUNT(..))和COUNT(DISTINCT(..))的区别相同。

<强>更新

检查生成的SQL后，我可以确认单独的count()和distinct()生成的查询为SELECT DISTINCT COUNT(..) ..，而countDistinct()的查询为SELECT COUNT(DISTINCT(..) ..。< / p>