实体框架查询未命中过滤索引WHERE BIT字段= 0

Question

I've noticed that Entity Framework translates LINQ queries with negative boolean filters such that the generated query plan won't use a filtered index. For example, the query:

context.Foo.Count(f => !f.IsActive)

generates the SQL statement:

SELECT 
    [GroupBy1].[A1] AS [C1]
    FROM ( SELECT 
        COUNT(1) AS [A1]
        FROM [dbo].[Foos] AS [Extent1]
        WHERE [Extent1].[IsActive] <> cast(1 as bit)
    )  AS [GroupBy1]

Notice the WHERE clause uses [IsActive] <> cast(1 as bit) , rather than the more intuitive [IsActive] = 0 . This becomes an issue when using filtered indexes. The plan for the above query will not use the following index:

CREATE INDEX IX_Foo_IsActive ON Foos (IsActive) WHERE (IsActive = 0)

I suspect the reason that EF generates queries this way has something to do with DB null semantics, but this happens even with non-nullable bit fields. I've verified that writing the filtered index with EF's syntax ( IsActive <> 1 ) fixes the issue, but that would break any non-EF queries using the more common syntax.

Is there a better work around?

Full example program here: http://dotnetfiddle.net/3kZugt . The entity type used above is:

public class Foo
{
    public int Id { get; set; }
    public bool IsActive { get; set; }
}

Answer 1

It's not unusual that for some strange reason, sometimes we don't see something which is really obvious: do a direct translation of your DB predicate to a C# predicate, ie

WHERE IsActive = 0

is translated to

f => f.IsActive = false

You have to stop thinking in C# and start thinking in SQL ;)