為了提高開發者的易用性,Rafy 領域實體框架在很早開始就已經支援使用 Linq 語法來查詢實體了。但是隻支援了一些簡單的、常用的條件查詢,支援的力度很有限。特別是遇到對聚合物件的查詢時,就不能再使用 Linq,而只能通過構造底層查詢樹的介面來完成了。由於開發者的聚合查詢的需求越來越多,所以本週我們將這部分進行了增強。
接下來,本文將說明 Rafy 框架原來支援的 Linq 語法,以及最新加入的聚合查詢支援及用法。
使用 Linq 查詢的程式碼示例
public WarehouseList GetByCode(string warehouseCode, string nameKeywords, PagingInfo pagingInfo)
{
return this.FetchList(r => r.DA_GetByCode(warehouseCode, nameKeywords, pagingInfo));
}
private EntityList DA_GetByCode(string warehouseCode, string nameKeywords, PagingInfo pagingInfo)
{
var q = this.CreateLinqQuery();
//條件對比
q = q.Where(e => e.Code == warehouseCode);
if (!string.IsNullOrEmpty(nameKeywords))
{
q = q.Where(e => e.Name.Contains(nameKeywords));
}
//排序
q = q.OrderByDescending(w => w.Name);
return this.QueryList(q, pagingInfo);//以指定的分頁資訊 pagingInfo 分頁
}
支援的一般查詢
使用 CreateLinqQuery 方法建立出一個 IQueryable<Warehouse> 物件,針對該物件,我們可以以下的標準 Linq 方法:Where、OrderBy、OrderByDescending、ThenBy、ThenByDescending、Count。
對於其中最重要的 Where 方法,Rafy 也支援許多操作,包括:
- 屬性的各種對比操作(=,!=,>,>=,<,<=,!,Contains,StartsWith,EndsWith等)。
- 支援兩個屬性條件間的連線條件:&&、||。
- 支援引用查詢。即間接使用引用實體的屬性來進行查詢,在生成 Sql 語句時,將會生成 INNER JOIN 語句,連線上這些被使用的引用實體對應的表。例如:
q = q.Where(warehouse => warehouse.Administrator.Name == "admin");
這部分的內容,之前的版本已經支援了,各位可參見 Rafy 框架的使用者手冊。
聚合查詢
聚合查詢的功能是,開發者可以通過定義聚合子的屬性的條件,來查詢聚合父。這是本次升級的重點。
例如,書籍管理系統中,Book (書)為聚合根,它擁有 Chapter (章)作為它的聚合子實體,而 Chapter 下則還有 Section(節)。那麼,我們可以通過這個功能,來查詢類似以下需求的資料:
- 查詢擁有某個章的名字的所有書籍。
要實現這種場景的查詢,我們可以在倉庫的資料層,使用下面的 Linq 語法:
public BookList LinqGetIfChildrenExists(string chapterName)
{
return this.FetchList(r => r.DA_LinqGetIfChildrenExists(chapterName));
}
private EntityList DA_LinqGetIfChildrenExists(string chapterName)
{
var q = this.CreateLinqQuery();
q = q.Where(book => book.ChapterList.Concrete().Any(c => c.Name == chapterName));
q = q.OrderBy(b => b.Name);
return this.QueryList(q);
}
其生成的 Sql 如下:
SELECT [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher] FROM [Book] AS [T0] WHERE EXISTS ( SELECT 1 FROM [Chapter] AS [T1] WHERE [T1].[BookId] = [T0].[Id] AND [T1].[Name] = @p0 ) ORDER BY [T0].[Name] ASC
- 查詢每個章的名字必須滿足某條件的所有書籍。
我們可以在倉庫的資料層,使用下面的 Linq 語法:
public BookList LinqGetIfChildrenAll(string chapterName)
{
return this.FetchList(r => r.DA_LinqGetIfChildrenAll(chapterName));
}
private EntityList DA_LinqGetIfChildrenAll(string chapterName)
{
var q = this.CreateLinqQuery();
q = q.Where(e => e.ChapterList.Cast<Chapter>().All(c => c.Name == chapterName));
q = q.OrderBy(e => e.Name);
return this.QueryList(q);
}
生成的 SQL 是:
SELECT [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher] FROM [Book] AS [T0] WHERE NOT (EXISTS ( SELECT 1 FROM [Chapter] AS [T1] WHERE [T1].[BookId] = [T0].[Id] AND [T1].[Name] != @p0 )) ORDER BY [T0].[Name] ASC
- 查詢某個章中所有節必須滿足某條件的所有書籍。
我們可以在倉庫的資料層,使用下面的 Linq 語法:
public BookList LinqGetIfChildrenExistsSectionName(string sectionName)
{
return this.FetchList(r => r.DA_LinqGetIfChildrenExistsSectionName(sectionName));
}
private EntityList DA_LinqGetIfChildrenExistsSectionName(string sectionName)
{
var q = this.CreateLinqQuery();
q = q.Where(book => book.ChapterList.Concrete().Any(c => c.SectionList.Cast<Section>().Any(s => s.Name.Contains(sectionName))));
q = q.OrderBy(b => b.Name);
return this.QueryList(q);
}
將會生成如下 SQL:
SELECT [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher] FROM [Book] AS [T0] WHERE EXISTS ( SELECT 1 FROM [Chapter] AS [T1] WHERE [T1].[BookId] = [T0].[Id] AND EXISTS ( SELECT 1 FROM [Section] AS [T2] WHERE [T2].[ChapterId] = [T1].[Id] AND [T2].[Name] LIKE @p0 ) ) ORDER BY [T0].[Name] ASC
- 同時,這些查詢也可以支援分頁。例如,我們在上面的查詢新增一個分頁條件,程式碼如下:
public BookList LinqGetIfChildrenExistsSectionName(string sectionName)
{
return this.FetchList(r => r.DA_LinqGetIfChildrenExistsSectionName(sectionName));
}
private EntityList DA_LinqGetIfChildrenExistsSectionName(string sectionName)
{
var q = this.CreateLinqQuery();
q = q.Where(book => book.ChapterList.Concrete().Any(c => c.SectionList.Cast<Section>().Any(s => s.Name.Contains(sectionName))));
q = q.OrderBy(b => b.Name);
return this.QueryList(q, new PagingInfo(2, 1));//分頁
}
分成的 SQL 如下:
SELECT TOP 1 [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher] FROM [Book] AS [T0] WHERE EXISTS ( SELECT 1 FROM [Chapter] AS [T1] WHERE [T1].[BookId] = [T0].[Id] AND EXISTS ( SELECT 1 FROM [Section] AS [T2] WHERE [T2].[ChapterId] = [T1].[Id] AND [T2].[Name] LIKE @p0 ) ) AND [T0].[Id] NOT IN ( SELECT TOP 1 [T0].[Id] FROM [Book] AS [T0] WHERE EXISTS ( SELECT 1 FROM [Chapter] AS [T1] WHERE [T1].[BookId] = [T0].[Id] AND EXISTS ( SELECT 1 FROM [Section] AS [T2] WHERE [T2].[ChapterId] = [T1].[Id] AND [T2].[Name] LIKE @p1 ) ) ORDER BY [T0].[Name] ASC ) ORDER BY [T0].[Name] ASC
頭暈,越來越複雜……不過經過測試,上面都沒有什麼問題。
下面是一個單元測試生成的分頁、複雜聚合查詢的 SQL,貼上來觀賞下:
SELECT TOP 2 [T0].[Id], [T0].[Author], [T0].[BookCategoryId], [T0].[BookLocId], [T0].[Code], [T0].[Name], [T0].[Price], [T0].[Publisher] FROM [Book] AS [T0] LEFT OUTER JOIN [BookCategory] AS [T1] ON [T0].[BookCategoryId] = [T1].[Id] WHERE [T0].[Name] != @p0 AND [T1].[Name] = @p1 AND EXISTS ( SELECT 1 FROM [Chapter] AS [T2] WHERE [T2].[BookId] = [T0].[Id] AND [T2].[Name] = @p2 ) AND EXISTS ( SELECT 1 FROM [Chapter] AS [T3] WHERE [T3].[BookId] = [T0].[Id] AND [T3].[Name] = @p3 AND NOT (EXISTS ( SELECT 1 FROM [Section] AS [T4] LEFT OUTER JOIN [SectionOwner] AS [T5] ON [T4].[SectionOwnerId] = [T5].[Id] WHERE [T4].[ChapterId] = [T3].[Id] AND ([T4].[Name] NOT LIKE @p4 OR [T4].[SectionOwnerId] IS NULL OR [T5].[Name] != @p5) )) ) AND [T0].[Id] NOT IN ( SELECT TOP 4 [T0].[Id] FROM [Book] AS [T0] LEFT OUTER JOIN [BookCategory] AS [T1] ON [T0].[BookCategoryId] = [T1].[Id] WHERE [T0].[Name] != @p6 AND [T1].[Name] = @p7 AND EXISTS ( SELECT 1 FROM [Chapter] AS [T2] WHERE [T2].[BookId] = [T0].[Id] AND [T2].[Name] = @p8 ) AND EXISTS ( SELECT 1 FROM [Chapter] AS [T3] WHERE [T3].[BookId] = [T0].[Id] AND [T3].[Name] = @p9 AND NOT (EXISTS ( SELECT 1 FROM [Section] AS [T4] LEFT OUTER JOIN [SectionOwner] AS [T5] ON [T4].[SectionOwnerId] = [T5].[Id] WHERE [T4].[ChapterId] = [T3].[Id] AND ([T4].[Name] NOT LIKE @p10 OR [T4].[SectionOwnerId] IS NULL OR [T5].[Name] != @p11) )) ) ORDER BY [T0].[Name] ASC ) ORDER BY [T0].[Name] ASC
剛開始支援 Linq 查詢的時候,就已經把聚合查詢的單元測試給寫了。鑑於比較複雜,所以一直沒有實現。這周總算完成了這部分程式碼,心中一塊石頭落了地。