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针对强类型数据集的慢速LINQ查询

strongly-typed-dataset search linq sql-server c#

birdus · 技术社区 · 9 年前

我有一个数据库,其中大约有5000行。还有许多多对多关系。作为“高级搜索”查询的一部分,我需要跨表进行自由文本搜索。

我创建了一个强类型数据集,并在应用程序启动时从SQL Server导入所有数据。对数据集执行LINQ查询时,查询执行速度非常慢(约15秒)。我认为对内存数据集执行查询要比SQL Server快得多,但事实似乎并非如此。我甚至需要在where子句中添加更多连接和“搜索”,所以事情只会变得更糟。

在我搜索的字段中,最长的是摘要,数据库中最长的字段不到2000字节,所以我们并不是说要搜索很多数据。我在这里选错了树了吗,或者有没有办法提高这个查询的性能?

代码如下:

var results = from e in _data.ds.Employee
      join es in _data.ds.EmployeeSkill on e.EmployeeId equals es.EmployeeId into esGroup from esItem in esGroup.DefaultIfEmpty()
      join s in _data.ds.Skill on esItem?.SkillId equals s.SkillId into sGroup from skillItem in sGroup.DefaultIfEmpty()
      join er in _data.ds.EmployeeRole on e.EmployeeId equals er.EmployeeId into erGroup from erItem in erGroup.DefaultIfEmpty()
      join r in _data.ds.Role on erItem?.RoleId equals r.RoleId into rGroup from rItem in rGroup.DefaultIfEmpty()
      join et in _data.ds.EmployeeTechnology on e.EmployeeId equals et.EmployeeId into etGroup from etItem in etGroup.DefaultIfEmpty()
      join t in _data.ds.Technology on etItem?.TechnologyId equals t.TechnologyId into tGroup from tItem in etGroup.DefaultIfEmpty()
      where
        e.FirstName.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0 ||
        e.LastName.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0 ||
        e.RMMarket.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0 ||
        !e.IsSummaryNull() && e.Summary.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0
      select new SearchResult
      {
          EmployeeId = e.EmployeeId,
          Name = e.FirstName + " " + e.LastName,
          Title = e.Title,
          ImageUrl = e.IsImageUrlNull() ? string.Empty : e.ImageUrl,
          Market = e.RMMarket,
          Group = e.Group,
          Summary = e.IsSummaryNull() ? string.Empty : e.Summary.Substring(1, e.Summary.Length < summaryLength ? e.Summary.Length - 1 : summaryLength),
          AdUserName = e.AdUserName
      };

2 回复 | 直到 9 年前

NetMage 9 年前

假设您仍然加载到 DataSet

预加入数据以用作搜索索引:

var searchBase = (from e in _data.ds.Employee
             join es in _data.ds.EmployeeSkill on e.EmployeeId equals es.EmployeeId into esGroup
             from esItem in esGroup.DefaultIfEmpty()
             join s in _data.ds.Skill on esItem?.SkillId equals s.SkillId into sGroup
             from skillItem in sGroup.DefaultIfEmpty()
             join er in _data.ds.EmployeeRole on e.EmployeeId equals er.EmployeeId into erGroup
             from erItem in erGroup.DefaultIfEmpty()
             join r in _data.ds.Role on erItem?.RoleId equals r.RoleId into rGroup
             from rItem in rGroup.DefaultIfEmpty()
             join et in _data.ds.EmployeeTechnology on e.EmployeeId equals et.EmployeeId into etGroup
             from etItem in etGroup.DefaultIfEmpty()
             join t in _data.ds.Technology on etItem?.TechnologyId equals t.TechnologyId into tGroup
             from tItem in etGroup.DefaultIfEmpty()
             select new {
                e.FirstName, e.LastName, e.RMMarket, e.Summary,
                e.EmployeeID, e.Title, e.ImageUrl, e.Group, e.AdUserName
             }).ToList();

对加载和连接的数据运行搜索:

var results = from e in searchBase
          where
                e.FirstName.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0 ||
                e.LastName.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0 ||
                e.RMMarket.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0 ||
                !e.IsSummaryNull() && e.Summary.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0
          select new SearchResult {
              EmployeeId = e.EmployeeId,
              Name = e.FirstName + " " + e.LastName,
              Title = e.Title,
              ImageUrl = e.IsImageUrlNull() ? string.Empty : e.ImageUrl,
              Market = e.RMMarket,
              Group = e.Group,
              Summary = e.IsSummaryNull() ? string.Empty : e.Summary.Substring(1, e.Summary.Length < summaryLength ? e.Summary.Length - 1 : summaryLength),
              AdUserName = e.AdUserName
          };

顺便说一句,您的示例代码没有显示进行连接的理由,因为在条件或答案中没有使用任何连接范围变量,而且您仍然需要连接每一个变量,因此只需将它们排除在外就是最快的解决方案。

Cory Nelson 9 年前

一些想法:

首先,您正在搜索字符串。如果要搜索的内容很多,请考虑维护全文索引以加快搜索速度。

第二,把 where join 条款。在LINQ语句中,过滤数据的内容应该尽可能高。目前,它正在为每一行加入一组数据,即使在以下情况下也不会使用它: 哪里 条款是错误的。