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我正在使用 Fluent NHibernate 的自动映射,并使用以下代码来确保 NHibernate 不会剥离毫秒:

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>();
    }
}

这工作得很好,因此数据正确地存储在数据库中。

但是,当我运行以下 LINQ 查询时,我没有得到预期的匹配:

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

生成的 SQL 如下所示,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?

顺便说一句,message.EventTag.TimeStamp是一个DateTimeOffset

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1 回答 1

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我被日志输出愚弄了: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:timestampPostgreSQL 中的列只有微秒精度,而DateTimeDiff这里的值为 16:51:30.5094984,这意味着 1/10 微秒精度。保持完整准确性的唯一方法似乎是将刻度存储在数据库中。

(让我感到困惑的另一个原因是我在不同线程上或多或少同时收到来自 MassTransit 的重复消息,因此检查数据库中的重复消息当然并不总是有效。哦,多线程的奇迹!)

于 2013-03-02T11:25:54.477 回答