多态性 – 在RavenDb中的多映射索引上按Clr-Type过滤

2019年8月3日 149次阅读

我在RavenDb中存储所有从基类继承的对象,并且我使用Multi-Map索引来搜索所有子类型,如下所示：

public class BaseRequest
{
    public Guid Id { get; set; }
    public string RequestName { get; set; }
    public DateTime RequiredDate { get; set; }
}

public class RequestA: BaseRequest
{
    public string SomethingForA { get; set; }
}

public class RequestB : BaseRequest
{
    public int SomethingForB { get; set; }
}

public class AllRequests: AbstractMultiMapIndexCreationTask
{
    public AllRequests()
    {
        AddMap<RequestA>(requests => from req in requests select new {req.RequestName, req.RequiredDate});
        AddMap<RequestB>(requests => from req in requests select new {req.RequestName, req.RequiredDate });
    }   
}

我这样搜索：

    public BaseRequest[] Search(string requestType, string requestName, DateTime? requestDate = null) {
        var q = RavenSession.Query<BaseRequest, AllRequests>();

        if (!string.IsNullOrEmpty(requestName)) {
            q = (IRavenQueryable<BaseRequest>)Queryable.Where(q, x => x.RequestName == requestName);
        }
        if (requestDate.HasValue) {
            q = (IRavenQueryable<BaseRequest>) Queryable.Where(q, x => x.RequiredDate == requestDate);
        }

        return q.ToArray();
    }

我想要做的是通过请求的CLR-Type进一步过滤结果.是否可以使用“Raven-Entity-Name”元数据字段执行此操作,如果是,如何执行此操作？

我知道我可以使用Query< RequestA>()等,但我可能需要在以后按多种类型进行过滤,这些类型将由用户动态选择.

注意：我真正想要做的是使用索引在给定某个RequestName的情况下撤回请求,但只返回RequestA(后来只返回RequestA,RequestC和RequestD).我不想做多个查询来单独返回每个类型,我想做一个查询按参数查询,有时输入.

系统的设计是为了让Requests类型每个月左右都会被添加,我们最终可能会有几百种不同的类型.我想用给定的参数动态搜索一组特定类型.

最佳答案 解决了这个问题.我需要使用MetadataFor(req)将clr类型添加到索引,然后使用特定的地图类型进行查询.像这样：

public class AllRequests: AbstractMultiMapIndexCreationTask
{
    public class SearchMap {
      public string RequestName{get;set;}
      public DateTime RequiredDate{get;set;}
      public string RequestType{get;set;}
    }

   public AllRequests(){
        AddMap<RequestA>(requests => from req in requests select new {req.RequestName, req.RequiredDate, RequestType = MetadataFor(req)["Raven-Clr-Type"]});
        AddMap<RequestB>(requests => from req in requests select new {req.RequestName, req.RequiredDate, RequestType = MetadataFor(req)["Raven-Clr-Type"] });
    }   
}

然后,我可以查询请求的实际字段,也可以按以下类型查询：

   public BaseRequest[] Search(string requestType, string requestName, DateTime? requestDate = null) {
        var q = RavenSession.Query<AllRequests.SearchMap, AllRequests>();

        if (!string.IsNullOrEmpty(requestName)) {
            q = (IRavenQueryable<BaseRequest>)Queryable.Where(q, x => x.RequestName == requestName);
        }
        if (requestDate.HasValue) {
            q = (IRavenQueryable<BaseRequest>) Queryable.Where(q, x => x.RequiredDate == requestDate);
        }

        if (!string.IsNullOrEmpty(requestType))
        {
            q =
                q.Where(
                    x =>
                    x.RequestType == GetClrTypeFromPassedInValue(requestType));
        }
        return q.As<BaseRequest>().ToArray();
    }
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