java - JPA 标准 - 依赖 WHERE 子句

Question

我正在尝试在 JPA Criteria 查询中创建以下查询:

SELECT V.* FROM VENDA V
WHERE 
( SELECT COUNT(D.ID) FROM VENDADETALHE D WHERE D.ID IN
( SELECT CVD.DETALHES_ID FROM VENDA_VENDADETALHE CVD WHERE CVD.VENDA_ID = V.ID ) 
AND ( SELECT I.TIPO FROM ITEM I WHERE I.ID=D.IDITEM ) <> 'SERVICO' ) = 0
AND
( SELECT COUNT(D.ID) FROM VENDADETALHE D WHERE D.ID IN
( SELECT CVD.DETALHES_ID FROM VENDA_VENDADETALHE CVD WHERE CVD.VENDA_ID = V.ID ) 
AND ( SELECT I.TIPO FROM ITEM I WHERE I.ID=D.IDITEM ) = 'SERVICO' ) > 0

我有以下类结构

public class Venda {
  /* other class attributes ( id & etc... ) */
  @OneToMany( orphanRemoval=true, cascade = CascadeType.ALL, fetch =FetchType.LAZY )
  @JoinTable
  private List<VendaDetalhe> detalhes;
}

public class VendaDetalhe{
  /* other class attributes */
  @ManyToOne
  @JoinColumn( name = "iditem", referencedColumnName = "id")
  private Item item;
}

public class Item{
  /* other class attributes */
  @Enumerated( EnumType.STRING )
  private ETipo tipo;
}
public enum ETipo{
  PRODUTO,
  SERVICO;
}

以及以下查询代码:

CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<Venda> qry = builder.createQuery( Venda.class );
Root<Venda> root = qry.from( Venda.class );
Join<Venda,VendaDetalhe> join = root.join( "detalhes", JoinType.INNER );
List<Predicate> p = new ArrayList<>();
p.add( builder.greatherThan( builder.count( builder.equal( join.get( "item" ).get("tipo"), ETipo.SERVICO ) ), 0L ) );
p.add( builder.equal( builder.count( builder.equal( join.get("item" ).get("tipo"),ETipo.PRODUTO) ), 0L) );
qry.where( p.toArray( new Predicate[ p.size() ] );
em.createQuery( qry ).getResultList();

但这会生成一个 QuerySyntaxException，表示需要 CLOSE，但发现了 =。我的 CriteriaQuery 语法正确吗？我在互联网上搜索了有关在 WHERE 子句上使用 count 的信息，但找不到任何内容。

异常消息如下:

org.hibernate.hql.internal.ast.QuerySyntaxException: expecting CLOSE, found '=' near line 1, 
column 249 
[select generatedAlias0 from
 br.com.koinonia.habil.model.user.movimentacoes.compraevenda.Venda 
as generatedAlias0 inner join generatedAlias0.detalhes as generatedAlias1 where 
( generatedAlias0.empresa=:param0 ) and ( count(generatedAlias1.item.tipo=:param1)>0L ) 
and ( count(generatedAlias1.item.tipo=:param2)=0L )]

Answer 1

Don't run a count query when you could run an exists query 。即使您停留在 SQL 语言(或任何翻译为 SQL 的语言，例如 JPQL)中，您的优化器也可能无法识别转换 COUNT(*) == 0的可能性。 code> 到 NOT EXISTS() 和 COUNT(*) > 0 到 EXISTS()。想象一下其中一个计数结果为 100 万。您真的需要数据库计算出准确计数值吗？或者数据库可以在知道是否存在(或不存在)给定行后立即停止吗？

您的原始查询可以重写为:

SELECT V.* 
FROM VENDA V
WHERE NOT EXISTS ( 
  SELECT 1 
  FROM VENDADETALHE D 
  WHERE D.ID IN ( 
    SELECT CVD.DETALHES_ID 
    FROM VENDA_VENDADETALHE CVD 
    WHERE CVD.VENDA_ID = V.ID 
  ) 
  AND ( 
    SELECT I.TIPO FROM ITEM I WHERE I.ID=D.IDITEM 
  ) <> 'SERVICO' 
)
AND EXISTS ( 
  SELECT 1 
  FROM VENDADETALHE D 
  WHERE D.ID IN ( 
    SELECT CVD.DETALHES_ID 
    FROM VENDA_VENDADETALHE CVD 
    WHERE CVD.VENDA_ID = V.ID 
  ) 
  AND ( 
    SELECT I.TIPO FROM ITEM I WHERE I.ID=D.IDITEM 
  ) = 'SERVICO' 
)

当然，与 'SERVICO' 进行比较的相关子查询可以进一步转换为内部联接，但我不确定这是否会造成问题。

也许，现在用 JPQL 编写更容易，但为什么不直接通过 EntityManager.createNativeQuery(String, Class) 运行 SQL 查询呢？ 。由于您正在投影一个实体 (V.*)，因此这可以正常工作。