Pourquoi Entity Framework ignore-t-il la méthode Take() lors de la génération de SQL?

Question

J'utilise les méthodes .Skip et .Take avec Entity Framework. L'appel .Skip est honoré lors de la génération du SQL. Le .Take n'est pas. Ce code:

 public IList<DocPullRun> GetDocRunsPaginated(int startRowIndex, int maximumRows) { 

     Logger.Debug("GetDocRunsPaginated: startRowIndex: {0}, maximumRows: {1}", startRowIndex, maximumRows); 
     Debug.Assert(startRowIndex >= 0); 
     IOrderedQueryable<DocPullRun> sortedPulls = 
      from run in DB.DocPullRuns 
       .Include("DocumentPullDefinition") 
       .Include("DocumentPullDefinition.Case") 
       .Include("DocumentPullDefinition.DocCategory") 
       .Include("DocumentPullDefinition.Repository") 
       .Include("DocumentPullDefinition.Repository.ConcordanceRepository") 

      orderby run.PullStarted descending 
      select run; 

     IQueryable<DocPullRun> query = sortedPulls.Skip(startRowIndex); 
     if (maximumRows > 0) 
      query.Take(maximumRows); 

     return query.ToList(); 
    } 

Les résultats dans ce SQL indiqué ci-dessous (notez que dans cet appel, startRowIndex est 0 et maximumRows est). La clause Where contient WHERE [Project1]. [Row_number]> 0 (qui est la partie .Skip), mais je m'attendais à voir un Sélectionnez TOP 10 mais au lieu de simplement voir un Select. La liste résultante a plus de 10 éléments. Notez que j'ai exécuté SQL Trace et que le SQL est en effet différé et pas réellement envoyé jusqu'à la dernière ligne: query.ToList(). Est-ce un type de bug?

SELECT 
[Project1].[C1] AS [C1], 
[Project1].[Id] AS [Id], 
[Project1].[PullStarted] AS [PullStarted], 
[Project1].[PullEnded] AS [PullEnded], 
[Project1].[MatchedQuery] AS [MatchedQuery], 
[Project1].[NewDocs] AS [NewDocs], 
[Project1].[UpdatedDocs] AS [UpdatedDocs], 
[Project1].[DeletedDocs] AS [DeletedDocs], 
[Project1].[Errors] AS [Errors], 
[Project1].[C2] AS [C2], 
[Project1].[Id1] AS [Id1], 
[Project1].[Requestor] AS [Requestor], 
[Project1].[RequestTime] AS [RequestTime], 
[Project1].[Query] AS [Query], 
[Project1].[Enabled] AS [Enabled], 
[Project1].[LastPullTime] AS [LastPullTime], 
[Project1].[Case_ID] AS [Case_ID], 
[Project1].[Case_Name] AS [Case_Name], 
[Project1].[Client_ID] AS [Client_ID], 
[Project1].[Matter_ID] AS [Matter_ID], 
[Project1].[Is_Active] AS [Is_Active], 
[Project1].[Requires_Case_Specific_Permissions] AS [Requires_Case_Specific_Permissions], 
[Project1].[Last_Update] AS [Last_Update], 
[Project1].[C3] AS [C3], 
[Project1].[Category_ID] AS [Category_ID], 
[Project1].[CategoryName] AS [CategoryName], 
[Project1].[DefaultGridLayout] AS [DefaultGridLayout], 
[Project1].[C4] AS [C4], 
[Project1].[Repository_ID] AS [Repository_ID], 
[Project1].[Description] AS [Description], 
[Project1].[OfficeAbbr] AS [OfficeAbbr], 
[Project1].[C5] AS [C5], 
[Project1].[Repository_ID1] AS [Repository_ID1], 
[Project1].[ConcordanceDBId] AS [ConcordanceDBId], 
[Project1].[Repository_ID2] AS [Repository_ID2], 
[Project1].[RepositoryType_Id] AS [RepositoryType_Id] 
FROM (SELECT [Project1].[Id] AS [Id], [Project1].[PullStarted] AS [PullStarted], [Project1].[PullEnded] AS [PullEnded], [Project1].[MatchedQuery] AS [MatchedQuery], [Project1].[NewDocs] AS [NewDocs], [Project1].[UpdatedDocs] AS [UpdatedDocs], [Project1].[DeletedDocs] AS [DeletedDocs], [Project1].[Errors] AS [Errors], [Project1].[Id1] AS [Id1], [Project1].[Requestor] AS [Requestor], [Project1].[RequestTime] AS [RequestTime], [Project1].[Query] AS [Query], [Project1].[Enabled] AS [Enabled], [Project1].[LastPullTime] AS [LastPullTime], [Project1].[Case_ID] AS [Case_ID], [Project1].[Case_Name] AS [Case_Name], [Project1].[Client_ID] AS [Client_ID], [Project1].[Matter_ID] AS [Matter_ID], [Project1].[Is_Active] AS [Is_Active], [Project1].[Requires_Case_Specific_Permissions] AS [Requires_Case_Specific_Permissions], [Project1].[Last_Update] AS [Last_Update], [Project1].[Category_ID] AS [Category_ID], [Project1].[CategoryName] AS [CategoryName], [Project1].[DefaultGridLayout] AS [DefaultGridLayout], [Project1].[Repository_ID] AS [Repository_ID], [Project1].[Description] AS [Description], [Project1].[OfficeAbbr] AS [OfficeAbbr], [Project1].[Repository_ID1] AS [Repository_ID1], [Project1].[ConcordanceDBId] AS [ConcordanceDBId], [Project1].[Repository_ID2] AS [Repository_ID2], [Project1].[RepositoryType_Id] AS [RepositoryType_Id], [Project1].[C1] AS [C1], [Project1].[C2] AS [C2], [Project1].[C3] AS [C3], [Project1].[C4] AS [C4], [Project1].[C5] AS [C5], row_number() OVER (ORDER BY [Project1].[PullStarted] DESC) AS [row_number] 
    FROM (SELECT 
     [Extent1].[Id] AS [Id], 
     [Extent1].[PullStarted] AS [PullStarted], 
     [Extent1].[PullEnded] AS [PullEnded], 
     [Extent1].[MatchedQuery] AS [MatchedQuery], 
     [Extent1].[NewDocs] AS [NewDocs], 
     [Extent1].[UpdatedDocs] AS [UpdatedDocs], 
     [Extent1].[DeletedDocs] AS [DeletedDocs], 
     [Extent1].[Errors] AS [Errors], 
     [Extent2].[Id] AS [Id1], 
     [Extent2].[Requestor] AS [Requestor], 
     [Extent2].[RequestTime] AS [RequestTime], 
     [Extent2].[Query] AS [Query], 
     [Extent2].[Enabled] AS [Enabled], 
     [Extent2].[LastPullTime] AS [LastPullTime], 
     [Extent3].[Case_ID] AS [Case_ID], 
     [Extent3].[Case_Name] AS [Case_Name], 
     [Extent3].[Client_ID] AS [Client_ID], 
     [Extent3].[Matter_ID] AS [Matter_ID], 
     [Extent3].[Is_Active] AS [Is_Active], 
     [Extent3].[Requires_Case_Specific_Permissions] AS [Requires_Case_Specific_Permissions], 
     [Extent3].[Last_Update] AS [Last_Update], 
     [Extent4].[Category_ID] AS [Category_ID], 
     [Extent4].[CategoryName] AS [CategoryName], 
     [Extent5].[DefaultGridLayout] AS [DefaultGridLayout], 
     [Extent6].[Repository_ID] AS [Repository_ID], 
     [Extent6].[Description] AS [Description], 
     [Extent6].[OfficeAbbr] AS [OfficeAbbr], 
     [Extent9].[Repository_ID] AS [Repository_ID1], 
     [Extent9].[ConcordanceDBId] AS [ConcordanceDBId], 
     [Extent12].[Repository_ID] AS [Repository_ID2], 
     [Extent13].[RepositoryType_Id] AS [RepositoryType_Id], 
     1 AS [C1], 
     1 AS [C2], 
     1 AS [C3], 
     1 AS [C4], 
     1 AS [C5] 
     FROM   [dbo].[DocPullRuns] AS [Extent1] 
     LEFT OUTER JOIN [dbo].[DocumentPullDefinitions] AS [Extent2] ON [Extent1].[DocumentPullDefinitionId] = [Extent2].[Id] 
     LEFT OUTER JOIN [dbo].[Cases] AS [Extent3] ON [Extent2].[CaseId] = [Extent3].[Case_ID] 
     LEFT OUTER JOIN [dbo].[DocCategories] AS [Extent4] ON [Extent2].[CategoryId] = [Extent4].[Category_ID] 
     LEFT OUTER JOIN [dbo].[DocCategories] AS [Extent5] ON [Extent2].[CategoryId] = [Extent5].[Category_ID] 
     LEFT OUTER JOIN [dbo].[Repositories] AS [Extent6] ON [Extent2].[RepositoryId] = [Extent6].[Repository_ID] 
     LEFT OUTER JOIN (SELECT [Extent7].[Repository_ID] AS [Repository_ID3], [Extent7].[RepositoryType_Id] AS [RepositoryType_Id], [Extent7].[Description] AS [Description], [Extent7].[OfficeAbbr] AS [OfficeAbbr], [Extent8].[Repository_ID] AS [Repository_ID4], [Extent8].[ConcordanceDBId] AS [ConcordanceDBId] 
      FROM [dbo].[Repositories] AS [Extent7] 
      LEFT OUTER JOIN [dbo].[ConcordanceRepositories] AS [Extent8] ON [Extent7].[Repository_ID] = [Extent8].[Repository_ID]) AS [Join6] ON [Extent2].[RepositoryId] = [Join6].[Repository_ID3] 
     LEFT OUTER JOIN [dbo].[ConcordanceRepositories] AS [Extent9] ON [Join6].[Repository_ID4] = [Extent9].[Repository_ID] 
     LEFT OUTER JOIN (SELECT [Extent10].[Repository_ID] AS [Repository_ID5], [Extent10].[RepositoryType_Id] AS [RepositoryType_Id], [Extent10].[Description] AS [Description], [Extent10].[OfficeAbbr] AS [OfficeAbbr], [Extent11].[Repository_ID] AS [Repository_ID6], [Extent11].[ConcordanceDBId] AS [ConcordanceDBId] 
      FROM [dbo].[Repositories] AS [Extent10] 
      LEFT OUTER JOIN [dbo].[ConcordanceRepositories] AS [Extent11] ON [Extent10].[Repository_ID] = [Extent11].[Repository_ID]) AS [Join9] ON [Extent2].[RepositoryId] = [Join9].[Repository_ID5] 
     LEFT OUTER JOIN [dbo].[ConcordanceRepositories] AS [Extent12] ON [Join9].[Repository_ID6] = [Extent12].[Repository_ID] 
     LEFT OUTER JOIN [dbo].[Repositories] AS [Extent13] ON [Extent2].[RepositoryId] = [Extent13].[Repository_ID] 
    ) AS [Project1] 
) AS [Project1] 
WHERE [Project1].[row_number] > 0 
ORDER BY [Project1].[PullStarted] DESC 

Answer 1

query.Take() ne mute pas la requête; il renvoie plutôt une nouvelle expression , que votre code ignore. Changez donc votre code pour:

if (maximumRows > 0) 
    query = query.Take(maximumRows); 

Answer 2

L'instruction if n'est pas nécessaire si vous ne voulez que le nombre maximum de lignes. S'il n'atteint pas le maximum, il retournera simplement tout ce qu'il recevra.

Vous pourriez dire:

return query.Take(maximumRows).ToList();