Weird Select/Delete query generation in Linq2SQL

Question

Hi

For some or other reason Linq2SQL generates the following on 1 of my tables for a delete:

DELETE FROM [dbo].[Tag] WHERE ([TagId] = @p0) AND ([Type] = @p1)
-- @p0: Input UniqueIdentifier (Size = 0; Prec = 0; Scale = 0) 
                               [fb538481-562d-45f2-bb33-3296cd7d0b28]
-- @p1: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [1]
-- @p2: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [0]
-- @p3: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [7]
-- @p4: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [5]
-- @p5: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [8]
-- @p6: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [4]
-- @p7: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [3]
-- @p8: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [9]
-- @p9: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [6]
-- @p10: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [1]
-- @p11: Input TinyInt (Size = 1; Prec = 0; Scale = 0) [2]
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel 
      Build: 3.5.30729.1

As one can see, the first 2 parameters (@p0 and @p1) are correct, but then it generates a randomized set of the unique number from 0 to 9.

Now this does not affect the query/behaviour in any way, I am just interested in whats going on here.

UPDATE:

Tag is a base class for Linq2SQL inheritence. It seems the extra parameters are the integer values of the discriminator (Type) of all the inherited types. If I remove inherited types, the extra parameters goes down.

UPDATE 2:

I have noticed this happens for SELECT's too.

SELECT 
    (CASE 
        WHEN EXISTS(
            SELECT NULL AS [EMPTY]
            FROM [Tag] AS [t0]
            WHERE ([t0].[TagId] = @p0) AND ([t0].[TagType] = @p1)
            ) THEN 1
        ELSE 0
     END) AS [value]
-- @p0: Input Guid (Size = 0; Prec = 0; Scale = 0) 
                   [60000000-0000-0000-0000-fe0000000025]
-- @p1: Input Byte (Size = 0; Prec = 0; Scale = 0) [25]
-- @p2: Input Byte (Size = 0; Prec = 0; Scale = 0) [0]
-- @p3: Input Byte (Size = 0; Prec = 0; Scale = 0) [10]
-- @p4: Input Byte (Size = 0; Prec = 0; Scale = 0) [28]
-- @p5: Input Byte (Size = 0; Prec = 0; Scale = 0) [13]
-- @p6: Input Byte (Size = 0; Prec = 0; Scale = 0) [27]
-- @p7: Input Byte (Size = 0; Prec = 0; Scale = 0) [1]
-- @p8: Input Byte (Size = 0; Prec = 0; Scale = 0) [2]
-- @p9: Input Byte (Size = 0; Prec = 0; Scale = 0) [3]
-- @p10: Input Byte (Size = 0; Prec = 0; Scale = 0) [4]
-- @p11: Input Byte (Size = 0; Prec = 0; Scale = 0) [5]
-- @p12: Input Byte (Size = 0; Prec = 0; Scale = 0) [6]
-- @p13: Input Byte (Size = 0; Prec = 0; Scale = 0) [7]
-- @p14: Input Byte (Size = 0; Prec = 0; Scale = 0) [8]
-- @p15: Input Byte (Size = 0; Prec = 0; Scale = 0) [9]
-- @p16: Input Byte (Size = 0; Prec = 0; Scale = 0) [11]
-- @p17: Input Byte (Size = 0; Prec = 0; Scale = 0) [12]
-- @p18: Input Byte (Size = 0; Prec = 0; Scale = 0) [14]
-- @p19: Input Byte (Size = 0; Prec = 0; Scale = 0) [15]
-- @p20: Input Byte (Size = 0; Prec = 0; Scale = 0) [16]
-- @p21: Input Byte (Size = 0; Prec = 0; Scale = 0) [17]
-- @p22: Input Byte (Size = 0; Prec = 0; Scale = 0) [18]
-- @p23: Input Byte (Size = 0; Prec = 0; Scale = 0) [19]
-- @p24: Input Byte (Size = 0; Prec = 0; Scale = 0) [20]
-- @p25: Input Byte (Size = 0; Prec = 0; Scale = 0) [21]
-- @p26: Input Byte (Size = 0; Prec = 0; Scale = 0) [22]
-- @p27: Input Byte (Size = 0; Prec = 0; Scale = 0) [23]
-- @p28: Input Byte (Size = 0; Prec = 0; Scale = 0) [24]
-- @p29: Input Byte (Size = 0; Prec = 0; Scale = 0) [26]
-- Context: SqlProvider(SqlCE) Model: AttributedMetaModel 
      Build: 3.5.30729.1

Just to note. I am using an enum for the discriminator, as per the MS examples.

UPDATE 3

Now I am running a SQL profiler, and I am seeing the following, and it's pretty worrying :(

exec sp_executesql N'SELECT 
    (CASE 
        WHEN EXISTS(
            SELECT NULL AS [EMPTY]
            FROM [Tag] AS [t0]
            WHERE ([t0].[TagId] = @p0) AND ([t0].[TagType] = @p1)
            ) THEN 1
        ELSE 0
     END) AS [value]',
N'@p0 uniqueidentifier,
@p1 tinyint,
@p2 tinyint,
@p3 tinyint,
@p4 tinyint,
@p5 tinyint,
@p6 tinyint,
@p7 tinyint,
@p8 tinyint,
@p9 tinyint,
@p10 tinyint,
@p11 tinyint,
@p12 tinyint,
@p13 tinyint,
@p14 tinyint,
@p15 tinyint,
@p16 tinyint,
@p17 tinyint,
@p18 tinyint,
@p19 tinyint,
@p20 tinyint,
@p21 tinyint,
@p22 tinyint,
@p23 tinyint,
@p24 tinyint,
@p25 tinyint,
@p26 tinyint,
@p27 tinyint,
@p28 tinyint,
@p29 tinyint,
@p30 tinyint,
@p31 tinyint,
@p32 tinyint',
@p0='60000000-0000-0000-0000-FE0000000025',
@p1=25,@p2=0,@p3=23,@p4=29,@p5=31,@p6=16,@p7=14,@p8=1,@p9=2,
@p10=3,@p11=4,@p12=5,@p13=6,@p14=7,@p15=8,@p16=9,@p17=10,@p18=11,
@p19=12,@p20=13,@p21=22,@p22=15,@p23=17,@p24=18,@p25=19,@p26=20,
@p27=21,@p28=27,@p29=24,@p30=26,@p31=30,@p32=28

Thanks

leppie

Answer 1

Very interesting - it looks like it couldn't decide whether it could use the primary key or not... what does the object model look like? No hand-crafted inheritance or anything?

Answer 2

Did you pass an enumerable collection instead of a scalar value for the parameter that gets converted into @p1?

Answer 3

Is TagId marked as your primary key in the DBML designer properties? To check, open the DBML file, click on the TagId property of the Tag class and view the properties.

Answer 4

Please delete the dbml file from the project, restart the visual studio and reconstruct the dbml file. Some times the visual studio caches the old versions of your sql table or stored procedures schema. This might help linq to process sql correctly.

Answer 5

This sounds like a bug somewhere in Linq2Sql. I think the extra parameters shouldn't be generated.

I think you should file a bug at Microsoft Connect on this.

Answer 6

Have you thought about peeking into the framework source code and debugging the scenario by yourself?

Since the source for the .NET Framework is finally available this is quite easy to achieve :)

Link: Configuring Visual Studio to Debug .NET Framework Source Code