性能:XmlReader或LINQ to XML

Question

我有一个150 MB的XML文件,在我的项目中用作DB.目前我正在用它XmlReader来阅读它的内容.我想知道在XmlReader这种情况下使用或LINQ to XML 是否更好.

请注意,我正在搜索此XML中的项目并显示搜索结果,因此可能需要很长时间或片刻.

Answer 1

如果您想要性能,请使用XMLReader.它不读取整个文件并在内存中构建DOM树.相反,它从磁盘读取文件并返回它在路上找到的每个节点.

通过快速谷歌搜索,我找到了XMLReader,LinqToXML和XDocument.Load的性能比较.

https://web.archive.org/web/20130517114458/http://www.nearinfinity.com/blogs/joe_ferner/performance_linq_to_sql_vs.html

Answer 2

我个人会使用Microsoft帮助文件中概述的流技术来使用Linq to Xml:http: //msdn.microsoft.com/en-us/library/system.xml.linq.xstreamingelement.aspx#Y1392

这是一个使用简单过滤器从200mb xml文件读取的快速基准测试:

var xmlFilename = "test.xml";

//create test xml file
var initMemoryUsage = GC.GetTotalMemory(true);
var timer = System.Diagnostics.Stopwatch.StartNew();
var rand = new Random();
var testDoc = new XStreamingElement("root", //in order to stream xml output XStreamingElement needs to be used for all parent elements of collection so no XDocument
    Enumerable.Range(1, 10000000).Select(idx => new XElement("child", new XAttribute("id", rand.Next(0, 1000))))
);
testDoc.Save(xmlFilename);
var outStat = String.Format("{0:f2} sec {1:n0} kb //linq to xml ouput streamed", timer.Elapsed.TotalSeconds, (GC.GetTotalMemory(false) - initMemoryUsage) / 1024);

//linq to xml not streamed
initMemoryUsage = GC.GetTotalMemory(true);
timer.Restart();
var col1 = XDocument.Load(xmlFilename).Root.Elements("child").Where(e => (int)e.Attribute("id") < 10).Select(e => (int)e.Attribute("id")).ToArray();
var stat1 = String.Format("{0:f2} sec {1:n0} kb //linq to xml input not streamed", timer.Elapsed.TotalSeconds, (GC.GetTotalMemory(false) - initMemoryUsage) / 1024);

//xmlreader
initMemoryUsage = GC.GetTotalMemory(true);
timer.Restart();
var col2 = new List<int>();
using (var reader = new XmlTextReader(xmlFilename))
{
    while (reader.ReadToFollowing("child"))
    {
        reader.MoveToAttribute("id");
        int value = Convert.ToInt32(reader.Value);
        if (value < 10)
            res2.Add(value);
    }
}
var stat2 = String.Format("{0:f2} sec {1:n0} kb //xmlreader", timer.Elapsed.TotalSeconds, (GC.GetTotalMemory(false) - initMemoryUsage) / 1024);

//linq to xml streamed
initMemoryUsage = GC.GetTotalMemory(true);
timer.Restart();
var col3 = StreamElements(xmlFilename, "child").Where(e => (int)e.Attribute("id") < 10).Select(e => (int)e.Attribute("id")).ToArray();
var stat3 = String.Format("{0:f2} sec {1:n0} kb //linq to xml input streamed", timer.Elapsed.TotalSeconds, (GC.GetTotalMemory(false) - initMemoryUsage) / 1024);

//util method
public static IEnumerable<XElement> StreamElements(string filename, string elementName)
{
    using (var reader = XmlTextReader.Create(filename))
    {
        while (reader.Name == elementName || reader.ReadToFollowing(elementName))
            yield return (XElement)XElement.ReadFrom(reader);
    }
}

这是我的机器上的处理时间和内存使用情况:

11.49 sec 225 kb      // linq to xml ouput streamed

17.36 sec 782,312 kb  // linq to xml input not streamed
6.52 sec 1,825 kb     // xmlreader
11.74 sec 2,238 kb    // linq to xml input streamed