EF can't infer return schema from Stored Procedure selecting from a #temp table

问题

Suppose the following:

CREATE PROCEDURE [MySPROC]
AS 
BEGIN

CREATE TABLE #tempSubset(
    [MyPrimaryKey] [bigint]  NOT NULL,
    [OtherColumn]  [int]     NOT NULL)

INSERT INTO #tempSubset (MyPrimaryKey, OtherColumn) 
    SELECT SomePrimaryKey, SomeColumn 
    FROM   SomeHugeTable
    WHERE  LimitingCondition = true

SELECT MyPrimaryKey, OtherColumn 
FROM   #tempSubset
WHERE  SomeExpensiveCondition = true

END

When I generate a function import or map a return type, EF doesn\'t generate a complex type or tells me:

The selected stored procedure or function returns no columns

How to overcome this?

Other answers suggest using table variables (not going to do this for performance reasons) faking the return schema and commenting out the real stored procedure, other suggest doing similar with views... but there must be a way to do this without having to add unnecessary overhead or requiring me to break a stored procedure to update the model?

回答1:

CREATE PROCEDURE [MySPROC]
AS 
BEGIN

--supplying a data contract
IF 1 = 2 BEGIN
    SELECT
        cast(null as bigint)  as MyPrimaryKey,
        cast(null as int)    as OtherColumn
    WHERE
        1 = 2  
END

CREATE TABLE #tempSubset(
    [MyPrimaryKey] [bigint]  NOT NULL,
    [OtherColumn]  [int]     NOT NULL)

INSERT INTO #tempSubset (MyPrimaryKey, OtherColumn) 
    SELECT SomePrimaryKey, SomeColumn 
    FROM   SomeHugeTable
    WHERE  LimitingCondition = true

SELECT MyPrimaryKey, OtherColumn 
FROM   #tempSubset
WHERE  SomeExpensiveCondition = true

END

Supplying a faux data contract for the result set is the easiest, cleanest and fastest way to take care of the issue. This same problem exists in data source controls in SSIS too. .NET will read the result set from the unreachable "contract" section of the query and supply the metadata for the complex type. No performance impact and no need to comment out the SQL that does the actual work.

回答2:

Adding this to the top of the stored procedure definition:

SET FMTONLY OFF

allowed the model to infer the schema from the temporary table without issue. As a bonus, it doesn't require additional maintenance for a contract.

Example:

SET FMTONLY OFF

CREATE TABLE #tempTable (
    ...
)

...

SELECT * FROM #tempTable

回答3:

Solution 1 Use a table variable instead of a temporary table.

Solution 2 Use the Set FMTONLY off; SQL command in the procedure and you will get the column information to create a new complex type.

Solution 3 This is not a good way, but it's a very easy way. Just add a select statement with dummy data and it will not execute because 1=0.

you can check details on this link

回答4:

This is incomplete but when set fmtonly off does not work, you can generate the data contract using the following:

        SELECT * 
        FROM tempdb.sys.columns 
        WHERE [object_id] = OBJECT_ID(N'tempdb..#u');

        select case  system_type_id 
        when 62 then 'cast(null as float) as ' 
        when 175 then 'cast(null as char(' + cast(max_length as varchar(50)) + ')) as ' 
        when 167 then 'cast(null as varchar(' + cast(max_length as varchar(50)) + ')) as ' 
        when 56 then 'cast(null as int) as ' 
        when 104 then 'cast(null as bit) as ' 
        when 106 then 'cast(null as decimal(' + cast(precision as varchar(50)) + ',' + cast(scale as varchar(50)) + ')) as ' 
        when 40 then 'cast(null as date) as '            
        end
        + name + ','
        from  tempdb.sys.columns 
        WHERE [object_id] = OBJECT_ID(N'tempdb..#u');

来源：https://stackoverflow.com/questions/16593473/ef-cant-infer-return-schema-from-stored-procedure-selecting-from-a-temp-table

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entity-framework