EF6 Oracle时间戳&日期 [英] EF6 Oracle TimeStamp & Date

问题描述

我开始将EntityFramework 6与Oracle(客户端12.x)一起使用. 我有几个带有DATE列和TIMESTAMP列的表.

I'm starting to use EntityFramework 6 with Oracle (client 12.x). I have severals tables with DATE columns and TIMESTAMP columns.

由EF6生成的所有查询都将.NET DateTime类型转换为TIMESTAMP.因此查询性能非常差.

All queries generated by EF6 convert .NET DateTime type to TIMESTAMP. So the query performance is very poor.

我尝试将DATETIME列的精度添加到0，但对生成的查询没有任何更改.

I tried to add a precision to 0 for the DATETIME columns but nothing changes on the generated query.

Property(_ => _.MyDate).HasColumnName("DATE_COLUMN").HasPrecision(0);

如何在代码中指定使用TO_DATE函数而不是TO_TIMESTAMP函数转换where子句?

How can I specify in my code to translate my where clause by a TO_DATE function and not by a TO_TIMESTAMP function ?

推荐答案

我在DATE Oracle类型和EF6.1上也遇到了类似的问题. 我的解决方法是使用 CodeFirstFunctions 库(仅适用于EF6.1和更高版本)，首先在Oracle中指定一个转换函数:

I've had a similar issue with DATE Oracle type and EF6.1. My workaround was to use the CodeFirstFunctions library (available only for EF6.1 and later) and specify a conversion function first in Oracle:

create or replace FUNCTION TO_DATE_LOCAL 
(
  DATETIMETOCONVERT IN VARCHAR2 
, CONVERTFORMAT IN VARCHAR2 
) RETURN DATE AS 
BEGIN
  RETURN to_date(DATETIMETOCONVERT, CONVERTFORMAT);
END TO_DATE_LOCAL;

稍后在我的DbContext中:

And later in my DbContext:

[DbFunction("CodeFirstDatabaseSchema", "TO_DATE_LOCAL")]
public static DateTime ToDateLocal(string dateTimeToConvert, string convertFormat)
{
    // no need to provide an implementation
    throw new NotSupportedException();
}

因此，我可以强制Entity Framework在where条件中使用DATE类型:

So I can force Entity Framework to use DATE type in a where condition:

var measurement = 
  context.Measurements
    .Where(m => m.MeasuredAt == 
          PlantContext.ToDateLocal("2016.01.01 10:00:00", "YYYY.MM.DD Hh24:MI:SS"))
    .FirstOrDefault();

如果使用Oracle，请小心使用带有CodeFirstFunctions的函数名称和模式名称的大写字母.

Be careful to use capital letters for the function name and for the schema name with CodeFirstFunctions if you use Oracle.

如果您需要更多详细信息，我已经写了一个博客文章并带有示例项目.

If you need more details I've written a blog post about this with an example project.

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