我有一个多地图索引，需要在Reduce结果中获得最大日期。
当我尝试：
Reduce = results => from result in results
group result by result.Id into g
select new
{
Id = g.Key,
AccountId = g.Select(x => x.AccountId).Where(x => x != null).FirstOrDefault(),
Hostnames = g.SelectMany(x => x.Hostnames),
NextRenewalDate = g.Select(x => x.NextRenewalDate).Max(),
SubscriptionCount = g.Sum(x => x.SubscriptionCount)
};
NextRenewalDate始终为空。
但是，我可以这样做：
NextRenewalDate = g.Select(x => x.NextRenewalDate).FirstOrDefault,
我确实得到了结果。
我想知道这是否是由于RavenDB如何解释索引中的日期。我的Reduce Result类如下：
public class ReduceResult
{
public string Id { get; set; }
public string AccountId { get; set; }
public string[] Hostnames { get; set; }
public DateTime NextRenewalDate { get; set; }
public int SubscriptionCount { get; set; }
}
我已经能够使索引工作，但前提是我将DateTime转换为ISO8601字符串。我的完整索引如下：
public class Account_Sites : AbstractMultiMapIndexCreationTask<Account_Sites.ReduceResult>
{
public Account_Sites()
{
AddMap<CMS.Domain.Site>(sites => from site in sites
from url in site.Urls
select new
{
Id = site.Id,
AccountId = (string)null,
Hostnames = new[] { url.Hostname },
SubscriptionDueDate = DateTime.MinValue,
SubscriptionStartDate = DateTime.MinValue
});
AddMap<Domain.Account>(accounts => from account in accounts
from siteId in account.Sites
from subscription in account.Subscriptions
where subscription != null
select new
{
Id = siteId,
AccountId = account.Id,
Hostnames = new string[0],
SubscriptionDueDate = subscription.NextRenewalDate,
SubscriptionStartDate = subscription.StartDate
});
Reduce = results => from result in results
group result by result.Id into g
select new
{
Id = g.Key,
AccountId = g.Select(x => x.AccountId).Where(x => x != null).FirstOrDefault(),
Hostnames = g.SelectMany(x => x.Hostnames),
SubscriptionDueDate = g.Max(x => x.SubscriptionDueDate.ToString("o")), // ISO 8601 format e.g. 2012-10-22T12:51:03.0263843+00:00
SubscriptionStartDate = g.Max(x => x.SubscriptionStartDate.ToString("o"))
};
}
public class ReduceResult
{
public string Id { get; set; }
public string AccountId { get; set; }
public string[] Hostnames { get; set; }
public DateTime SubscriptionDueDate { get; set; }
public DateTime SubscriptionStartDate { get; set; }
}
}
我在下面发布了一个完整的失败测试。丹尼尔的测试确实有效，但以下失败了。但是，将TestSubscription.EndDate更改为DateTime.Now（而不是UtcNow）确实有效。这是使用构建 1.2.2103-Unstable 。
public class TestAccount
{
public string Id { get; set; }
public List<string> Sites { get; set; }
public List<TestSubscription> Subscriptions { get; set; }
public TestAccount()
{
Sites = new List<string>();
Subscriptions = new List<TestSubscription>();
}
}
public class TestSubscription
{
public DateTime EndDate { get; set; }
}
public class TestSite
{
public string Id { get; set; }
public string Hostname { get; set; }
}
public class SitesWithSubscriptions : AbstractMultiMapIndexCreationTask<SitesWithSubscriptions.Result>
{
public SitesWithSubscriptions()
{
AddMap<TestSite>(sites => from site in sites
select new
{
SiteId = site.Id,
Hostname = site.Hostname,
SubscriptionEndDate = DateTime.MinValue
});
AddMap<TestAccount>(accounts => from account in accounts
from siteId in account.Sites
from subscription in account.Subscriptions
select new
{
SiteId = siteId,
Hostname = (string)null,
SubscriptionEndDate = subscription.EndDate
});
Reduce = results => from result in results
group result by result.SiteId into g
select new
{
SiteId = g.Key,
Hostname = g.Select(x => x.Hostname).Where(x => x != null).FirstOrDefault(),
SubscriptionEndDate = g.Max(x => x.SubscriptionEndDate)
};
}
public class Result
{
public string SiteId { get; set; }
public string Hostname { get; set; }
public DateTime SubscriptionEndDate { get; set; }
}
}
public class SitesSpecs : RavenSpecs
{
static IEnumerable<SitesWithSubscriptions.Result> results;
Establish ctx = () =>
{
using (var session = Store.OpenSession())
{
var site = new TestSite { Hostname = "www.dev.com" };
session.Store(site);
var account = new TestAccount();
account.Subscriptions.Add(new TestSubscription { EndDate = DateTime.UtcNow });
account.Sites.Add(site.Id);
session.Store(account);
session.SaveChanges();
}
};
Because of = () =>
{
using (var session = Store.OpenSession())
{
results = session.Query<SitesWithSubscriptions.Result, SitesWithSubscriptions>()
.Customize(x => x.WaitForNonStaleResults())
.ToList();
}
};
It Should_return_sites_with_subscription_end_dates = ()
=>
{
results.Count().ShouldEqual(1);
results.First().SubscriptionEndDate.Date.ShouldEqual(DateTime.UtcNow.Date);
};
}
答案 0 :(得分：3)
这是一个快速的例子，展示了如何做到这一点：
更新：我编写了这段代码来验证RavenDB可以按照您的要求处理DateTime。您不需要将其转换为ISO中的字符串，...我在Build 960中尝试过它。如果它不适合您，请提供失败的测试并让我们知道您正在使用哪个版本。
public class Student
{
public string Id { get; set; }
public string Classroom { get; set; }
public DateTime Birthday { get; set; }
}
public class LatestBirthdayInClassroom : AbstractIndexCreationTask<Student, LatestBirthdayInClassroom.Result>
{
public class Result
{
public string Classroom { get; set; }
public DateTime LatestBirthday { get; set; }
}
public LatestBirthdayInClassroom()
{
Map = students => from student in students
select new
{
Classroom = student.Classroom,
LatestBirthday = student.Birthday
};
Reduce = results => from result in results
group result by result.Classroom into g
select new
{
Classroom = g.Key,
LatestBirthday = g.Select(x => x.LatestBirthday).Max()
};
}
}
class Program
{
static void Main(string[] args)
{
using (var store = new EmbeddableDocumentStore
{
RunInMemory = true
}.Initialize())
{
using (var session = store.OpenSession())
{
session.Store(new Student { Classroom = "A", Birthday = new DateTime(2012, 2, 1) });
session.Store(new Student { Classroom = "A", Birthday = new DateTime(2012, 5, 1) });
session.Store(new Student { Classroom = "A", Birthday = new DateTime(2012, 3, 1) });
session.Store(new Student { Classroom = "B", Birthday = new DateTime(2012, 8, 1) });
session.Store(new Student { Classroom = "B", Birthday = new DateTime(2012, 11, 1) });
session.Store(new Student { Classroom = "B", Birthday = new DateTime(2012, 9, 1) });
session.SaveChanges();
}
new LatestBirthdayInClassroom().Execute(store);
// wait for indexing
while (store.DatabaseCommands.GetStatistics().StaleIndexes.Length > 0)
{
Thread.Sleep(100);
}
using (var session = store.OpenSession())
{
var results = session.Query<LatestBirthdayInClassroom.Result, LatestBirthdayInClassroom>()
.ToList();
}
}
}
}
答案 1 :(得分：1)
这是RavenDB中的一个错误，已在build 2145中修复。http://issues.hibernatingrhinos.com/issue/RavenDB-718
的详细信息