Question

我正在使用Fluent NHibernate自动化，并使用以下代码来确保NHibernate不会消除毫秒：

public class TimestampTypeConvention : IPropertyConvention, IPropertyConventionAcceptance
{
    public void Accept(IAcceptanceCriteria<IPropertyInspector> criteria)
    {
        criteria.Expect(x => x.Type == typeof(DateTime) || x.Type == typeof(DateTimeOffset));
    }

    public void Apply(IPropertyInstance instance)
    {
        instance.CustomType<TimestampType>();
    }
}

这非常有效，因此数据可以正确存储在数据库中。

但是，当我运行以下LINQ查询时，我没有得到我期望的匹配：

bool isDuplicate = session.Query<TagData>()
                          .Any(x => x.TagName == message.EventTag.TagName
                               && x.TimeStamp == message.EventTag.TimeStamp.UtcDateTime);

生成的SQL看起来像这样，并解释了为什么这不起作用：

select tagdata0_."Id" as column1_0_, tagdata0_."TagName" as column2_0_,
tagdata0_."TimeStamp" as column3_0_, tagdata0_."Value" as column4_0_,
tagdata0_."QualityTimeStamp" as column5_0_, tagdata0_."QualitySubstatus" as column6_0_,
tagdata0_."QualityExtendedSubstatus" as column7_0_, tagdata0_."QualityLimit" as column8_0_,
tagdata0_."QualityDataSourceError" as column9_0_, tagdata0_."QualityTagStatus" as column10_0_,
tagdata0_."TagType" as column11_0_ from "TagData" tagdata0_
where tagdata0_."TagName"=:p0 and tagdata0_."TimeStamp"=:p1 limit 1;
:p0 = 'VALVE_HW_CMD' [Type: String (0)],
:p1 = 01.03.2013 16:51:30 [Type: DateTime (0)]

如何强制生成的查询使用完整精度？

BTW，message.EventTag.TimeStamp是DateTimeOffset

Answer 1

我被日志记录输出所迷惑：实际的SQL（取自PostgreSQL日志文件）如下所示：

SELECT this_."Id" as column1_0_0_, this_."TagName" as column2_0_0_,
this_."TimeStamp" as column3_0_0_, this_."Value" as column4_0_0_,
this_."QualityTimeStamp" as column5_0_0_, this_."QualitySubstatus" as column6_0_0_,
this_."QualityExtendedSubstatus" as column7_0_0_, this_."QualityLimit" as column8_0_0_,
this_."QualityDataSourceError" as column9_0_0_, this_."QualityTagStatus" as column10_0_0_,
this_."TagType" as column11_0_0_ FROM "TagData" this_
WHERE this_."TimeStamp" = ((E'2013-03-01 16:51:30.509498')::timestamp)

这就是它没有按预期工作的真正原因：PostgreSQL中的timestamp列只有微秒精度，而DateTimeDiff这里的值为16：51：30.5094984，其中意味着1/10微秒精度。保持完整准确性的唯一方法似乎是将滴答存储在数据库中。

（我混淆的另一个原因是我在不同的线程上或多或少同时收到了来自MassTransit的重复消息，因此检查数据库中的重复项当然并不总是有效.O，多线程的奇迹！）

在NHibernate中使用Timestamp列比较的LINQ查询

1 个答案: