如何批量从项目列表中获取子项目？

问题描述：

我有一个搜索方法，它返回多个项目，每个项目都带有几个引用其他表的子属性。对于作为集合的儿童财产，一切都按照我想要的方式工作，但我怎样才能为一对一的孩子做同样的事情？如何批量从项目列表中获取子项目？

下面是一些存根和一些代码的我尝试：

public class Request { 
    //HasMany(x => x.Examinations).Access.CamelCaseField().Cascade.All().BatchSize(100); 
    public virtual IList<Examination> Examinations; 

    //References(x => x.Creator, "rem_creator_userid"); 
    public virtual User Creator { get; private set; } 
} 

public class RepositoryExample { 

    // This search will ask one nice-looking query to the database fetchning all the 
    // requests 
    // Then it will ask ONE query fetching the Examinations from the database 
    // Then it will ask N+1 questions fetching Creator from all Requests 
    public IList<Request> Search1(ListRequestSearchConditions searchConditions) { 
     var query = 
      from request in Session.Query<Request>() 
      from exam in request.Examinations 
      where 
       searchConditions.Units.Contains(request.ReferralSource) && 
       exam.Status.HasValue && 
       exam.Status.Value >= ExaminationStatus.Value.RequestSubmitted && 
       request.PatientId != null 
      select request; 

     return query 
      .Skip((searchConditions.Page - 1) * searchConditions.PageSize) 
      .Take(searchConditions.PageSize) 
      .ToList(); 
    } 

    // This search with ask one slow join-query fetching everything from the database 
    public IList<Request> Search2(ListRequestSearchConditions searchConditions) { 
      Examination examinationAlias = null; 

     return Session.QueryOver<Request>() 
      .WhereRestrictionOn(request => request.ReferralSource).IsIn(searchConditions.Units) 
      .Where(request => request.PatientId != null) 
      .JoinAlias(request => request.Examinations,() => examinationAlias) 
      .Where(() => examinationAlias.Status.Value != null) 
      .Where(() => examinationAlias.Status.Value >= ExaminationStatus.Value.RequestSubmitted) 
      .Skip((searchConditions.Page - 1) * searchConditions.PageSize) 
      .Take(searchConditions.PageSize) 
      .ToList(); 
    } 

    // This search will first ask ONE query joining Request with Examinations 
    // Then it will ask ONE query fetching the Examinations from the database 
    // Then it will ask N+1 queries fetching Creator from all Requests 
    public IList<Request> Search3(ListRequestSearchConditions searchConditions) { 
      Examination examinationAlias = null; 

     return Session.QueryOver<Request>() 
      .WhereRestrictionOn(request => request.ReferralSource).IsIn(searchConditions.Units) 
      .Where(request => request.PatientId != null) 
      .JoinAlias(request => request.Examinations,() => examinationAlias) 
      .Where(() => examinationAlias.Status.Value != null) 
      .Where(() => examinationAlias.Status.Value >= ExaminationStatus.Value.RequestSubmitted) 
      .Fetch(request => request.Examinations).Lazy 
      .Fetch(request => examinationAlias.ExaminationType).Lazy; 
      .Skip((searchConditions.Page - 1) * searchConditions.PageSize) 
      .Take(searchConditions.PageSize) 
      .ToList(); 
    } 
}

我希望能够做到这一点的3个查询，一个读取请求的列表，一个获取考试和一个取的创作者。

答

如果您不希望在单个查询中使用它（在LINQ中使用Fetch/ThenFetch）并使用批处理，则必须在Creator映射级别指定它。批量大小无法在查询级别定义。

在流利的NHibernate中，您可以在Creator映射中添加BatchSize(100)。

BATCHSIZE（）不适用于一个一对一的映射，其创建者是如此。 – 2012-03-27 18:57:07

将其添加到创建者实体级别上，而不是关系级别上。 – NOtherDev 2012-03-28 09:54:51

非常感谢，不知道你可以在实体级别设置批量大小！ – 2012-03-28 10:25:38

答

尽在其中，如果没有一招地方我不能使用往返

// determine the requests 
var subquery = QueryOver.Of<Request>() 
    .WhereRestrictionOn(request => request.ReferralSource).IsIn(searchConditions.Units) 
    .Where(request => request.PatientId != null) 
    .JoinQueryOver(request => request.Examinations) 
    .Where(examination => examination.Status.Value != null) 
    .Where(examination => examinationAlias.Status.Value >= ExaminationStatus.Value.RequestSubmitted) 
    .Skip((searchConditions.Page - 1) * searchConditions.PageSize) 
    .Take(searchConditions.PageSize) 
    .Select(r => r.Id); 

// load the requests with eagerly fetching the associations 
var results = Session.QueryOver<Request>() 
    .WithSubquery.WhereProperty(request => request.Id).In(subquery) 
    .Fetch(request => request.Creator).Eager 
    .Fetch(request => request.Examinations).Eager 
    .ToList();

如何批量从项目列表中获取子项目？

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