[英]Slow LINQ query against strongly typed Dataset
我有一个包含约5,000行的数据库。 还有许多多对多的关系。 我需要跨表进行自由文本搜索,作为“高级搜索”查询的一部分。
我创建了一个强类型的数据集,并在应用启动时从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(大约15秒)。 我以为对内存中的数据集执行查询会比SQL Server快得多,但事实并非如此。 我什至需要在where子句中添加更多的联接和“搜索”,所以情况只会变得更糟。
在我要搜索的字段中,最长的是摘要,数据库中最长的是小于2,000字节,因此我们并不是在谈论要搜索的大量数据。 我是不是在这里树错了树,还是有办法提高此查询的性能?
这是代码:
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
};
一些想法:
首先,您要搜索字符串。 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。
其次,将where
子句放在join
子句之前。 过滤数据的内容在LINQ语句中应尽可能高。 它当前正在为每一行加入一堆数据,即使where
子句为false也不使用它。
假设您仍然加载到DataSet
而不是对象列表中(没有足够的信息来翻译该部分),这是我的建议:
预加入要用作搜索索引的数据:
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();
针对已加载和联接的数据运行搜索:
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,您的示例代码没有任何理由进行联接,因为没有联接范围变量在条件或答案中使用,并且无论如何您都将每个联接都联接在一起,因此,将它们排除在外将是最快的解决方案。
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