Question

我有两张桌子：

发票（InvoiceID，InvoiceNumber）
发票_产品（InvoiceID，ProductID，IsFinalized）

我显示所有发票的清单，并且有按钮可以按“已完成”或“未最终确定”的发票进行过滤。最终确定的发票是上的每个产品IsFinalized==true。

目前我的代码执行速度非常慢：

IEnumerable<Invoice> invoices = db.Invoices;

if (isFinalized) // filter by finalized invoices
{
    List<Invoice> unfinalizedInvoices = new List<Invoice>();

    foreach (var invoice in invoices)
    {
        int invoicesProductsCountTotal = db.Invoices_Products.Where(l => l.InvoiceID == invoice.InvoiceID).Count();
        int invoicesProductsCountFinalized = db.Invoices_Products.Where(l => l.InvoiceID == invoice.InvoiceID && l.IsFinalized == true).Count();

        if (invoicesProductsCountTotal != invoicesProductsCountFinalized)
        {
            unfinalizedInvoices.Add(invoice);
        }
    }

    invoices = invoices.Except(unfinalizedInvoices);
}
else
{
    List<Invoice> finalizedInvoices = new List<Invoice>();

    foreach (var invoice in invoices)
    {
        int invoicesProductsCountTotal = db.Invoices_Products.Where(l => l.InvoiceID == invoice.InvoiceID).Count();
        int invoicesProductsCountFinalized = db.Invoices_Products.Where(l => l.InvoiceID == invoice.InvoiceID && l.IsFinalized == true).Count();

        if (invoicesProductsCountTotal == invoicesProductsCountFinalized && invoicesProductsCountFinalized > 0)
        {
            finalizedInvoices.Add(invoice);
        }
    }

    invoices = invoices.Except(finalizedInvoices);
}

我意识到这不是最佳的，但我喜欢传播我的LINQ，以便我能够阅读和理解它。
我的问题：有什么方法可以让我的查询更快使用.All或.Any或其他什么，或者我是否需要重新考虑我的数据库设计（可能在发票表中添加一个额外的列）

修改：第三个表是产品（ProductID，ProductNumber），但您知道

Answer 1

您现在正在加载所有发票，然后为每张发票加载产品。这肯定会很慢（当你开始添加大量发票时它会变慢很多）。

您应该在EntityFramework中创建多对多关系。（见example）

您的课程将如下所示：

class Invoice 
{
    List<Product> Products {get; set;}
}
class Product
{
    bool IsFinalized {get; set;}
}

现在您可以使用LINQ来确保只执行只获取所需数据的SQL语句：

var invoices = db.Invoices.Where(i => i.Products.All(p => p.IsFinalized == finalized));

Answer 2

迭代每个Invoice，然后向数据库发出其他请求将非常缓慢。让您的查询立即获取所有信息，然后迭代结果。

var result = from invoice in db.Invoices
             join invoicedProduct in db.Invoices_Products
               on invoice.InvoiceId equals invoicedProduct.InvoiceId
             select new
             {
                 InvoiceId = invoice.InvoiceId,
                 ProductId = invoicedProduct.ProductId,
                 IsFinalized = invoicedProuct.IsFinalized
             };

var grpResult = from record in result
                group record by record.ProductId into productGrp
                select productGrp;

foreach( var grp in grpResult )
{
    Console.WriteLine( "ProductId: " + grp.Key.ToString( ) );
    Console.WriteLine( "TotalCount: " + grp.Count( ).ToString( ) );
    Console.WriteLine( "Finalized: " + grp.Where( item => item.IsFinalized ).Count( ).ToString( ) );
}

Answer 3

if (isFinalized)
{
    invoices = invoices.Where(l => l.Invoices_Products.All(m => m.IsFinalized == true));
}
else
{
    List<Invoice> finalizedInvoices = invoices.Where(l => l.Invoices_Products.All(m => m.IsFinalized == true)).ToList();
    invoices = invoices.Except(finalizedInvoices);
}

^^这似乎大大改善了性能。哦，谢谢你的聆听

优化LINQ而不是创建新的集合/循环

3 个答案: