Stored Procedure runs fast after recompile

Question

I have a very weird issue with a stored procedure on SQL Server 2008 R2. Sometimes, about once every month, I have one procedure that becomes very slow, takes about 6sec to run instead of a few milliseconds. But if I simply recompile it, without changing anything, it runs fast again. It does not happen on all stored procedure, only one (there are a few hundreds on the server).

My guess is when the sp is compiled, it is cached and this cache is reused every time I call it, and this cached version gets corrupted for some reason.

I hoped maybe some people already faced this kind of issue, or could at least point me in the right direction, like what configuration of SQL Server or IIS could affect the stored procedure cache ?

Here's the code:

USE [MyBaseName]
GO
/****** Object:  StoredProcedure [dbo].[Publication_getByCriteria]    Script Date: 05/29/2013 12:11:07 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[Publication_getByCriteria]
    @id_sousTheme As int = null,
    @id_theme As int = null,
    @nbPubli As int = 1000000,
    @bActuSite As bit = null,
    @bActuPerso As bit = null,
    @bActuNewsletter As bit = null,
    @bActuChronique As bit = null,
    @bActuVideo As bit = null,
    @bActuVideoBuzz As bit = null,
    @bActuOpportunite As bit = null,
    @id_contact As int = null,
    @bOnlyPublished As bit = 0,
    @bOnlyForHomePage as bit = 0,
    @id_contactForTheme As int = null,
    @id_newsletter As int = null,
    @ID_ActuChronique As int = null,
    @sMotClef As varchar(500) = null,
    @sMotClefForFullText as varchar(500) = '""',
    @dtPublication As datetime = null,  
    @bParlonsFinance As bit = null,
    @bPartenaires as bit = null,
    @bUne As bit = null,
    @bEditoParlonsFinance As bit = null,
    @bEditoQuestionFonds as bit = null,
    @dtDebPublication As datetime = null,
    @dtFinPublication As datetime = null,
    @bOnlyActuWithDroitReponse As bit = 0,
    @bActuDroitReponse As bit = null
AS
BEGIN
    SET NOCOUNT ON;

    DECLARE @dtNow As datetime
    SET @dtNow = GETDATE()

    SELECT TOP (@nbPubli) p.id_publication, p.sTitre, p.sTexte, p.sTexteHTML, p.dtPublication, p.id_linkedDroitReponse,
        si.id_actusite, pe.id_actuPerso, ne.id_actuNewsletter, ac.id_actuChronique, av.id_actuVideo, ap.id_actuOpportunite, ad.id_actuDroitReponse,
        c.ID_Contact, c.sPhotoCarre, NULL As sTypePubli, n.id_newsletter, 
        dbo.Publication_get1Theme(p.id_publication) As theme,
        CAST(CASE WHEN ad.id_actuDroitReponse IS NULL THEN 0 ELSE 1 END As bit) As bIsDroitReponse,
        coalesce(Personne.sNom, Societe.sNom) as sNom, Personne.sPrenom
    FROM Publication p
        LEFT OUTER JOIN ActuSite si ON p.id_publication = si.id_publication
        LEFT OUTER JOIN ActuPerso pe ON p.id_publication = pe.id_publication
        LEFT OUTER JOIN ActuNewsletter ne ON p.id_publication = ne.id_publication
        LEFT OUTER JOIN ActuChronique ac ON p.id_publication = ac.id_publication
        LEFT OUTER JOIN ActuVideo av ON p.id_publication = av.id_publication
        LEFT OUTER JOIN ActuOpportunite ap ON p.id_publication = ap.id_publication
        LEFT OUTER JOIN ActuDroitReponse ad ON p.id_publication = ad.id_publication
        LEFT OUTER JOIN Contact c ON p.id_contact = c.ID_Contact
        LEFT OUTER JOIN Personne ON Personne.id_contact = c.id_contact
        LEFT OUTER JOIN Societe ON Societe.id_contact = c.id_contact
        LEFT OUTER JOIN Newsletter n ON ne.id_actuNewsletter = n.id_actuNewsletter
    WHERE p.bSupp = 0
    AND (@bOnlyPublished = 0 Or (@bOnlyPublished = 1 AND p.dtPublication IS NOT NULL AND p.dtPublication < @dtNow))
    AND (@id_sousTheme IS NULL Or p.id_publication IN(SELECT id_publication FROM PubliSousTheme WHERE id_soustheme = @id_sousTheme))
    AND (@id_theme IS NULL Or p.id_publication IN(SELECT id_publication FROM PubliTheme WHERE id_theme = @id_theme))
    AND ((@bActuSite = 1 AND si.id_actusite IS NOT NULL)
            OR (@bActuPerso = 1 AND pe.id_actuPerso IS NOT NULL)
            OR (@bActuNewsletter = 1 AND ne.id_actuNewsletter IS NOT NULL)
            OR (@bActuChronique = 1 AND ac.id_actuChronique IS NOT NULL)
            OR (@bActuVideo = 1 AND av.id_actuVideo IS NOT NULL)
            OR (@bActuVideoBuzz = 1 AND av.id_actuVideo IS NOT NULL and coalesce(av.sBuzz, '') <> '' )
            OR (@bActuOpportunite = 1 AND ap.id_actuOpportunite IS NOT NULL)
            OR (@bActuDroitReponse = 1 AND ad.id_actuDroitReponse IS NOT NULL))
    AND (@id_contact IS NULL Or p.id_contact = @id_contact)
    AND (@id_contactForTheme IS NULL Or 
            (p.id_publication IN(SELECT id_publication FROM PubliSousTheme 
                WHERE id_soustheme IN(SELECT id_soustheme FROM ContactSousTheme WHERE id_contact = @id_contactForTheme)))
            Or (p.id_publication IN(SELECT id_publication FROM PubliTheme 
                WHERE id_theme IN(SELECT id_theme FROM ContactTheme WHERE id_contact = @id_contactForTheme)))
            )
    AND (@ID_ActuChronique is NULL or id_actuChronique = @ID_ActuChronique)
    AND (@id_newsletter IS NULL Or p.id_publication IN(SELECT id_publication FROM ListActuNewsletter WHERE id_newsletter = @id_newsletter))
    AND (@sMotClef IS NULL 
        or contains((p.sTexte, p.sTitre), @sMotClefForFullText)
        Or Personne.sNom LIKE '%' + @sMotClef + '%' COLLATE Latin1_General_CI_AI
        Or Personne.sPrenom LIKE '%' + @sMotClef + '%' COLLATE Latin1_General_CI_AI
        Or Societe.sNom LIKE '%' + @sMotClef + '%' COLLATE Latin1_General_CI_AI
        )
    AND (@dtPublication IS NULL Or p.dtPublication >= @dtPublication)
    AND (
        @bParlonsFinance IS NULL Or
        (@bParlonsFinance = 0 AND p.id_publication NOT IN(SELECT id_publication FROM PubliTheme 
                WHERE id_theme IN(SELECT id_theme FROM Theme WHERE bParlonsFinance = 1)))
        Or (@bParlonsFinance = 1 AND p.id_publication IN(SELECT id_publication FROM PubliTheme 
                WHERE id_theme IN(SELECT id_theme FROM Theme WHERE bParlonsFinance = 1))))
    AND (
        @bPartenaires IS NULL Or
        (@bPartenaires = 0 AND p.id_publication NOT IN(SELECT id_publication FROM PubliTheme 
                WHERE id_theme IN(SELECT id_theme FROM Theme WHERE 0 = 1)))
        Or (@bPartenaires = 1 AND p.id_publication IN(SELECT id_publication FROM PubliTheme 
                WHERE id_theme IN(SELECT id_theme FROM Theme WHERE 0 = 1))))
    AND (
        @bUne IS NULL
        Or p.bUne = @bUne)
    AND (@bEditoParlonsFinance IS NULL
        Or p.bEditoParlonsFinance = @bEditoParlonsFinance)
        AND (@bEditoQuestionFonds IS NULL
        Or p.bEditoQuestionFonds = @bEditoQuestionFonds)
    AND (@dtDebPublication IS NULL Or p.dtPublication >= @dtDebPublication)
    AND (@dtFinPublication IS NULL Or p.dtPublication <= @dtFinPublication)
    AND (@bOnlyActuWithDroitReponse = 0 Or (@bOnlyActuWithDroitReponse = 1 AND p.id_linkedDroitReponse IS NOT NULL))
    and (@bOnlyForHomePage = 0 or (@bOnlyForHomePage = 1 and ac.bHomePage = 1))
    ORDER BY coalesce(p.dtPublication, p.dtCreate) DESC, p.id_publication DESC
END

Solution 1

When you first compile a stored procedure, its execution plan gets cached.

If the sproc has parameters whose definitions can significantly change the contained query's execution plan (e.g. index scans vs seeks), the stored procedure's cached plan may not work best for all parameter definitions.

One way to avoid this is to include a RECOMPILE clause with the CREATE PROCEDURE statement.

Example:

CREATE PROCEDURE dbo.mySpro
@myParam
WITH RECOMPILE
AS
BEGIN
 -- INSERT WORKLOAD HERE
END
GO

By doing this, a new plan will be generated each time the procedure is called. If recompile time < time lost by its using the wrong cached plan, this is worth using WITH RECOMPILE. In your case, it will also save you the time/planning required to manually recompile this procedure every time you notice it is executing slowly.

Solution 2

For a stored procedure with that many parameters, it would be wise to add OPTION(OPTIMIZE FOR UNKNOWN) at the end of the query to tell the compiler not to optimize the execution plan for specific parameters.

What SQL Server does the first time it runs a stored procedure is optimize the execution plan(s) for the parameters that were passed to it. This is done in a process that is called Parameter Sniffing.

In general, execution plans are cached by SQL Server so that SQL Server doesn't have to recompile each time for the same query. The next time the procedure is run, SQL Server will re-use the execution plan(s) for the queries in it... However, the execution plan(s) might be totally inefficient if you call the stored procedure with different parameters.

Adding the option I mentioned will tell to the SQL compiler that the execution plan should not be optimized for specific parameters, but rather for any parameter that is passed to the stored procedure. From the documentation:

OPTIMIZE FOR UNKNOWN

Instructs the query optimizer to use statistical data instead of the initial values for all local variables when the query is compiled and optimized, including parameters created with forced parameterization.

The answer by @sion_corn recommends adding WITH RECOMPILE to the stored procedure definition, however this forces a recompile of the whole statement each time the stored procedure is executed. This might incur an unacceptable overhead if the procedure is called very often.