Rafy 中的 Linq 查询支持（根据聚合子条件查询聚合父）

时间:2022-04-25
本文章向大家介绍Rafy 中的 Linq 查询支持（根据聚合子条件查询聚合父），主要内容包括其使用实例、应用技巧、基本知识点总结和需要注意事项，具有一定的参考价值，需要的朋友可以参考一下。

为了提高开发者的易用性，Rafy 领域实体框架在很早开始就已经支持使用 Linq 语法来查询实体了。但是只支持了一些简单的、常用的条件查询，支持的力度很有限。特别是遇到对聚合对象的查询时，就不能再使用 Linq，而只能通过构造底层查询树的接口来完成了。由于开发者的聚合查询的需求越来越多，所以本周我们将这部分进行了增强。

接下来，本文将说明 Rafy 框架原来支持的 Linq 语法，以及最新加入的聚合查询支持及用法。

使用 Linq 查询的代码示例 

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();

    //条件对比
    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);//以指定的分页信息 pagingInfo 分页
}

支持的一般查询

使用 CreateLinqQuery 方法创建出一个 IQueryable<Warehouse> 对象，针对该对象，我们可以以下的标准 Linq 方法：Where、OrderBy、OrderByDescending、ThenBy、ThenByDescending、Count。

对于其中最重要的 Where 方法，Rafy 也支持许多操作，包括：

  • 属性的各种对比操作（=,!=,>,>=,<,<=,!,Contains,StartsWith,EndsWith等）。
  • 支持两个属性条件间的连接条件：&&、||。
  • 支持引用查询。即间接使用引用实体的属性来进行查询，在生成 Sql 语句时，将会生成 INNER JOIN 语句，连接上这些被使用的引用实体对应的表。例如： q = q.Where(warehouse => warehouse.Administrator.Name == "admin"); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }

这部分的内容，之前的版本已经支持了，各位可参见 Rafy 框架的用户手册。

聚合查询

聚合查询的功能是，开发者可以通过定义聚合子的属性的条件，来查询聚合父。这是本次升级的重点。

例如，书籍管理系统中，Book （书）为聚合根，它拥有 Chapter （章）作为它的聚合子实体，而 Chapter 下则还有 Section（节）。那么，我们可以通过这个功能，来查询类似以下需求的数据：

  • 查询拥有某个章的名字的所有书籍。

要实现这种场景的查询，我们可以在仓库的数据层，使用下面的 Linq 语法：

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
  • 查询每个章的名字必须满足某条件的所有书籍。

我们可以在仓库的数据层，使用下面的 Linq 语法：

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);
}
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
  • 查询某个章中所有节必须满足某条件的所有书籍。

我们可以在仓库的数据层，使用下面的 Linq 语法：

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);
}

将会生成如下 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
  • 同时，这些查询也可以支持分页。例如，我们在上面的查询添加一个分页条件，代码如下： 
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));//分页
}

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

头晕，越来越复杂……不过经过测试，上面都没有什么问题。

下面是一个单元测试生成的分页、复杂聚合查询的 SQL，贴上来观赏下：

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

刚开始支持 Linq 查询的时候，就已经把聚合查询的单元测试给写了。鉴于比较复杂，所以一直没有实现。这周总算完成了这部分代码，心中一块石头落了地。

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