查询运行速度快，存储过程慢-尝试了多种操作

Question

I have a stored procedure on SQL Server 2014 and when running the query directly with the params hard coded, it runs instantly. When its run through the stored procedure it takes a long time or times out.

It appears the parameters in the select query where its getting the top 1

  , ISNULL((SELECT TOP 1 block_score FROM block_states BS WHERE BS.block_id = defined_blocks.id AND BS.user_name = @local_userName AND BS.orgId = @local_orgId AND BS.assessment_key = 0 ), 'NONE' )

that is causing the problems as I have hardcoded these params in the stored procedure and it runs almost instantly.

I have read a lot about parameter sniffing and as suggested in Query runs fast, but runs slow in stored procedure and have tried a few things; I have made the parameters local ones I have also tried adding the

OPTION(RECOMPILE)

and tried running

exec sp_updatestats 

but all appeared to make either no or very little difference.

The stored procedure is as follows:

     @userName NVARCHAR(100), @orgId NVARCHAR(100),@ chartId INT
AS



    DECLARE @definedchartBlocks TABLE(
        chartId INT,
        sectId BIGINT,
        subsectId BIGINT,
        blockId BIGINT,
        blockScore NVARCHAR(10)

    )
        Declare  @local_userName NVARCHAR(100), @local_orgId NVARCHAR(100), @local_chartId INT
        select @local_userName=@userName, @local_orgId=@orgId,@local_chartId=@chartId /*attempt to speed up stp*/


    INSERT INTO @definedchartBlocks

    SELECT      
        defined_sects.chart_id
        , defined_subsects.sect_id
        , defined_blocks.subsect_id
        , defined_blocks.id AS blockId

        , ISNULL((SELECT TOP 1 block_score FROM block_states BS WHERE BS.block_id = defined_blocks.id AND BS.user_name = @local_userName AND BS.orgId = @local_orgId AND BS.assessment_key = 0 ), 'NONE' )
    FROM         
        defined_subsects 
        INNER JOIN
        defined_sects ON defined_subsects.sect_id = defined_sects.id 
        INNER JOIN
        defined_blocks ON defined_subsects.id = defined_blocks.subsect_id
    WHERE     
        (defined_sects.chart_id = @local_chartId)

OPTION(RECOMPILE)

    IF EXISTS (
    SELECT      
            MAX(definedchartBlocks.blockScore)
    FROM         
        @definedchartBlocks definedchartBlocks
    WHERE
        definedchartBlocks.blockScore = 'AMBER' OR definedchartBlocks.blockScore = 'RED' OR definedchartBlocks.blockScore = 'NONE' OR definedchartBlocks.blockScore = '' OR definedchartBlocks.blockScore IS NULL

    GROUP BY 
        definedchartBlocks.blockScore
    )
    BEGIN

        SELECT 0 AS chartCompleted
    END
    ELSE
    BEGIN
        SELECT 1 AS chartCompleted
    END

Answer 1

SQL Server does do a good job for the most part with implicit casts, but there are times that it can bog a query down. You mentioned that hard-coding the values returns instantly, but using a variable does not.

When using a variable, make sure that the datatype matches the column's datatype. I suspect that the issue is that your variables are NVARCHAR (100) whilst your columns are VARCHAR (50) .

Another way to see if this might be an issue is by looking at the query plan - in such a case, you might see something similar to the following as a warning:

Type conversion in expression (CONVERT_IMPLICIT(...)) may affect "SeekPlan" in query plan choice