C# 如何提高查询性能
我的数据库中大约有C# 如何提高查询性能,c#,mysql,entity-framework,C#,Mysql,Entity Framework,我的数据库中大约有100万数据(MySQL) 还有一个高级搜索功能,速度非常慢(超过30秒),因为生成的SQL EntityFramework不是很好,SQL: SELECT `Project1`.* FROM ( SELECT `Extent1`.* FROM `tnews` AS `Extent1` WHERE `Extent1`.`Region` = 'Americas(2)' ) AS `Project1` ORDER BY `Project1`.`PnetDT` DESC L
100万
数据(MySQL
)
还有一个高级搜索功能,速度非常慢(超过30秒),因为生成的SQL EntityFramework不是很好,SQL:
SELECT
`Project1`.*
FROM
(
SELECT
`Extent1`.*
FROM `tnews` AS `Extent1`
WHERE `Extent1`.`Region` = 'Americas(2)'
) AS `Project1`
ORDER BY
`Project1`.`PnetDT` DESC LIMIT 0,20
C#功能:
private List<CNNews> AdvancedSearchAndPage(int pagenum, int pagesize,
AdvSearchArgs advArgs)
{
IQueryable<CNNews> result = _dbRawDataContext.CNNews.
OrderByDescending(n => n.PnetDT);
if (!string.IsNullOrWhiteSpace(advArgs.Feed))
{
result = result.Where(news => news.Feed == advArgs.Feed);
}
if (!string.IsNullOrWhiteSpace(advArgs.PNET))
{
result = result.Where(news=>news.PNET == advArgs.PNET);
}
if (!string.IsNullOrWhiteSpace(advArgs.ProdCode))
{
result = (from news in result
where news.ProdCode == advArgs.ProdCode
select news);
}
if (!string.IsNullOrWhiteSpace(advArgs.Code))
{
result = (from news in result
where news.Code == advArgs.Code
select news);
}
if (!string.IsNullOrWhiteSpace(advArgs.BegineDate))
{
var begin = Convertion.ToDate(advArgs.BegineDate);
var end = Convertion.ToDate(advArgs.EndDate);
result = (from news in result
where news.PnetDT >= begin && news.PnetDT < end
select news);
}
if (!string.IsNullOrWhiteSpace(advArgs.Region))
{
result = result.Where(x => x.Region == advArgs.RegionName);
}
var pagedList = result.
Skip(pagenum * pagesize).
Take(pagesize);
return pagedList.ToList();
}
您可以直接从数据库集执行自己的SQL,并获得EF的所有好处,请参阅 还有其他方法,请参阅这些答案以了解更多详细信息
生成查询的LINQ如下所示:
IQueryable<CNNews> result = _dbRawDataContext.CNNews
.OrderByDescending(n => n.PnetDT)
.Where(x => x.Region == advArgs.RegionName)
.Skip(pagenum * pagesize)
.Take(pagesize);
另外,我不知道更改OrderByDescending()
和Skip()
/Take()
的顺序是否会产生不同的结果
(免责声明:我没有测试过)是。你凭什么认为我没有?嗯。。。你看过问题了吗?听起来你肯定是在问性能问题,而if子句与性能无关。这就是问题所在,你可以试一试。查看楼下的答案尝试以下操作:将
OrderByDescending()
从方法的顶部移动到底部:IQueryable result=\u dbRawDataContext.CNNews
和var pagedList=result.OrderByDescending().Skip(…
。我认为这将提高您的性能(这就是我在回答中试图说的)。
IQueryable<CNNews> result = _dbRawDataContext.CNNews
.OrderByDescending(n => n.PnetDT)
.Where(x => x.Region == advArgs.RegionName)
.Skip(pagenum * pagesize)
.Take(pagesize);
IQueryable<CNNews> result = _dbRawDataContext.CNNews
.Where(x => x.Region == advArgs.RegionName)
.OrderByDescending(n => n.PnetDT)
.Skip(pagenum * pagesize)
.Take(pagesize);