Extra SQL calls after EF6 upgrade

Question

I've recently noticed some extra sql calls when using miniprofiler.

They only seem to occur after a build, and I think they appeared after upgrading to EF6.

Are they just checking for changes in models?

And can I safely ignore them?

SELECT 
    [GroupBy1].[A1] AS [C1]
    FROM ( SELECT 
        COUNT(1) AS [A1]
        FROM [dbo].[__MigrationHistory] AS [Extent1]
    )  AS [GroupBy1]



SELECT 
    [GroupBy1].[A1] AS [C1]
    FROM ( SELECT 
        COUNT(1) AS [A1]
        FROM [dbo].[__MigrationHistory] AS [Extent1]
        WHERE ([Extent1].[ContextKey] = @p__linq__0) AND (@p__linq__0 IS NOT NULL)
    )  AS [GroupBy1]


SELECT TOP (1) 
    [Project1].[C1] AS [C1], 
    [Project1].[MigrationId] AS [MigrationId], 
    [Project1].[Model] AS [Model]
    FROM ( SELECT 
        [Extent1].[MigrationId] AS [MigrationId], 
        [Extent1].[Model] AS [Model], 
        1 AS [C1]
        FROM [dbo].[__MigrationHistory] AS [Extent1]
        WHERE ([Extent1].[ContextKey] = @p__linq__0) AND (@p__linq__0 IS NOT NULL)
    )  AS [Project1]
    ORDER BY [Project1].[MigrationId] DESC

Answer 1

These DB calls refer to the new Migration HIstory Table feature included in EF6 when using Code-First:

Migrations history table is a table used by Code First Migrations to store details about migrations applied to the database. By default the name of the table in the database is __MigrationHistory and it is created when applying the first migration do the database. In Entity Framework 5 this table was a system table if the application used Microsoft Sql Server database. This has changed in Entity Framework 6 however and the migrations history table is no longer marked a system table.

If you aren't using them, these calls shouldn't cause any harm. You can always disable them or have EF create DB change scripts for you instead.