Querydsl: when groupBy with two fields,fetchCount throw exception

[DannySnow]

here is my code:

query.groupBy(_entity.field1,_entity.field2).fetchCount()

then the exception:

java.lang.IllegalArgumentException: org.hibernate.hql.internal.ast.QuerySyntaxException: expecting CLOSE, found ',' near line 1, column 56 [select count(distinct entity.field1, entity.field2)
from com.demo.core.domain.model.entity entity
where entity.field3 = ?1

    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:133)
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:157)
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:164)
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:670)
    at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:23)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:305)
    at com.sun.proxy.$Proxy119.createQuery(Unknown Source)
    at com.querydsl.jpa.impl.AbstractJPAQuery.createQuery(AbstractJPAQuery.java:101)
    at com.querydsl.jpa.impl.AbstractJPAQuery.fetchCount(AbstractJPAQuery.java:81)
    at com.demo.core.infrastructure.repository.impl.queryRepositoryImpl.query(queryRepositoryImpl.java:91)
    at com.demo.core.infrastructure.repository.impl.queryRepositoryImplTest.query(queryRepositoryImplTest.java:25)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73)
    at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.hibernate.hql.internal.ast.QuerySyntaxException: expecting CLOSE, found ',' near line 1, column 56 [select count(distinct entity.field1, entity.field2)
from com.demo.core.domain.model.rebate.entity entity
where entity.field3 = ?1
    at org.hibernate.hql.internal.ast.QuerySyntaxException.convert(QuerySyntaxException.java:74)
    at org.hibernate.hql.internal.ast.ErrorCounter.throwQueryException(ErrorCounter.java:91)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.parse(QueryTranslatorImpl.java:291)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:186)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:141)
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:115)
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:77)
    at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:153)
    at org.hibernate.internal.AbstractSharedSessionContract.getQueryPlan(AbstractSharedSessionContract.java:553)
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:662)
    ... 41 more

and when I remove one field in the groupBy, the same code will success

so what's the problem?

[duc3d-hus]

I have same problem. Please help!

[jwgmeligmeyling]

fetchCount() uses a COUNT function, which is an aggregate function. Your query already has aggregate functions. You cant aggregate aggregate functions, unless a subquery is used (which is not available in JPA). Therefore this use case cannot be supported.

[jwgmeligmeyling]

Duplicate of #2053

[gudaoxuri]

My temporary solution

@SneakyThrows
protected <E> Page<E> pageDTOs(JPAQuery<E> jpaQuery, Long pageNumber, Integer pageSize) {
    if (jpaQuery.getMetadata().getGroupBy().size() > 1) {
        // Fixed https://github.com/querydsl/querydsl/pull/2605/files
        // Get JPQLSerializer
        var serializer = (JPQLSerializer) $.bean.invoke(jpaQuery,
                JPAQueryBase.class.getDeclaredMethod("serialize", boolean.class), false);
        String hql = serializer.toString();
        // HQL to Native SQL
        var translatorFactory = new ASTQueryTranslatorFactory();
        var hibernateSession = entityManager.getEntityManagerFactory().unwrap(SessionFactory.class);
        var translator = translatorFactory.
                createQueryTranslator("", hql, Collections.EMPTY_MAP, hibernateSession.getSessionFactory(), null);
        translator.compile(Collections.EMPTY_MAP, false);
        var sql = translator.getSQLString();
        // Package COUNT
        var countSql = "select count(1) from (" + sql + ") _tmp_" + System.currentTimeMillis();
        var nativeQuery = entityManager.createNativeQuery(countSql);
        // Add sql parameters
        JPAUtil.setConstants(nativeQuery, serializer.getConstantToAllLabels(), jpaQuery.getMetadata().getParams());
        // Fetch total number
        var totalNumber = ((BigInteger) (nativeQuery.getSingleResult())).longValue();
        // Fetch paginated records
        var objs = jpaQuery
                .limit(pageSize)
                .offset(pageNumber == 1 ? 0 : pageNumber * pageSize)
                .fetch();
        return Page.build(pageNumber, pageSize, totalNumber, objs);
    } else {
        var objs = jpaQuery
                .limit(pageSize)
                .offset(pageNumber == 1 ? 0 : pageNumber * pageSize)
                .fetchResults();
        return Page.build(pageNumber, pageSize, objs.getTotal(), objs.getResults());
    }
}

[jwgmeligmeyling]

That approach works only with Hibernate - not plain JPA, and only if there is a one-to-one mapping between your HQL parameters and SQL parameters, which isn't always the case (for example when a named parameter is reused in the query).

If you need reliable count queries I encourage you to use Blaze-Persistence, which has an awesome mechanism of converting any query to its count query. It also integrates with Querydsl (the blaze-persistence-querydsl module): https://persistence.blazebit.com/documentation/1.5/core/manual/en_US/index.html#querydsl-integration .

Using a BlazeJPAQuery instead of a JPAQuery both fetchResults and fetchCount work reliably again.

[tamilzh]

When should we expect a fix for 2504

[jwgmeligmeyling]

Not, its going to be removed as it cannot be implemented.

[Rossolinyisanautist]

Why this is not mentioned in the documentation? How are people supposed to use it?

[jwgmeligmeyling]

Because this method was originally intended for just querydsl-sql and was ported over to JPA very poorly. It inherently can't be supported in JPA, and therefore we will log warnings in the future.

I guess the answer is: don't rely on querydsl-jpa to make your count queries for you, use blaze-persistence-querydsl instead.

I've updated the javadoc with the rationale and alternatives: https://github.com/querydsl/querydsl/pull/2605/files#diff-63e9a52b83b73925263ae9ef7ad9372d4e76e8eceb9b2233139325bee46d8605R81-R102