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我创建了一个带有返回 Querydsl BooleanExpressions 的静态方法的类，因此我可以简单地将这些表达式传递给我的 Spring Data 存储库中的findAll()orfindOne()方法，并在我的应用程序中重用它们。像这里：http ://www.petrikainulainen.net/programming/spring-framework/spring-data-jpa-tutorial-part-five-querydsl/ 。

我遇到的问题是从我的方法返回的 BooleanExpression 正在生成似乎不是最佳的查询（至少对我而言）。

返回 BooleanExpression 的方法：

public static BooleanExpression byExternalIdAndProviderId(
     final String externalId, final Long providerId) {

  QEListing listing = QEListing.eListing;

  return listing.externalIds.any().externalId.equalsIgnoreCase(externalId)
        .and(listing.externalIds.any().provider.id.eq(providerId));
}

生成的查询：

select elisting0_.id as id1_24_, 
    elisting0_.address1 as address2_24_, 
    elisting0_.address2 as address3_24_, 
    elisting0_.business_name as business4_24_, 
    elisting0_.city_id as city10_24_, 
    elisting0_.created_date as created5_24_, 
    elisting0_.latitude as latitude6_24_, 
    elisting0_.longitude as longitud7_24_, 
    elisting0_.master_ext_id as master11_24_, 
    elisting0_.modified_date as modified8_24_, 
    elisting0_.state_id as state12_24_, 
    elisting0_.zip as zip13_24_, 
    elisting0_.zip_4 as zip9_24_, 
    elisting0_1_.vanity_name as vanity1_34_, 
    elisting0_2_.account_id as account1_2_ 
from listings elisting0_ 
    left outer join vanity_names elisting0_1_ on elisting0_.id=elisting0_1_.listing_id 
    left outer join accounts_to_listings elisting0_2_ on elisting0_.id=elisting0_2_.listing_id 
where (
    exists (
        select 1 
        from external_ids eexternali1_ 
        where (
            eexternali1_.id in (
                select externalid2_.external_id 
                from listing_to_external_id externalid2_ 
                where elisting0_.id=externalid2_.listing_id)) 
                and lower(eexternali1_.external_id)='123456'
        )
    ) 
and (
    exists (
        select 1 
        from external_ids eexternali3_ 
        where (
            eexternali3_.id in (
                select externalid4_.external_id 
                from listing_to_external_id externalid4_ 
                where elisting0_.id=externalid4_.listing_id
            )
        ) 
        and eexternali3_.provider_id=1
    )
)

与这样的事情相反：

select elisting0_.id as id1_24_, 
    elisting0_.address1 as address2_24_, 
    elisting0_.address2 as address3_24_, 
    elisting0_.business_name as business4_24_, 
    elisting0_.city_id as city10_24_, 
    elisting0_.created_date as created5_24_, 
    elisting0_.latitude as latitude6_24_, 
    elisting0_.longitude as longitud7_24_, 
    elisting0_.master_ext_id as master11_24_, 
    elisting0_.modified_date as modified8_24_, 
    elisting0_.state_id as state12_24_, 
    elisting0_.zip as zip13_24_, 
    elisting0_.zip_4 as zip9_24_, 
    elisting0_1_.vanity_name as vanity1_34_, 
    elisting0_2_.account_id as account1_2_ 
from listings elisting0_ 
    left outer join vanity_names elisting0_1_ on elisting0_.id=elisting0_1_.listing_id 
    left outer join accounts_to_listings elisting0_2_ on elisting0_.id=elisting0_2_.listing_id 
    join listing_to_external_id a on elisting0_.id = a.listing_id
    join external_ids b on a.external_id = b.id
where lower(b.external_id) = '123456'
and b.provider_id = 1

有什么方法可以生成更优化的查询，同时仍然提供 BooleanExpressions 的可重用性，并且还使用 Spring Data 的存储库？

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1 回答 1

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可能有更优化的方法，但不能使用连接，因为它们会修改结果集。因此，如果您找到优化 Querydsl 中的 any() 子查询的方法，请在 GitHub 问题跟踪器中创建票证。

如果 Querydsl 的使用仅限于谓词，则无法控制连接。

于 2013-05-31T06:07:33.020 回答