发现其中包含由子集使用RavenDB和LINQ的至少一种元素的对象 [英] Finding objects which contains at least one element from subset using RavenDB and LINQ

问题描述

我有简单类型问题：

public class Question
{
    public Question(string id)
    {
        Id = id;
        Tags = new List<string>();
    }

    public string Id { get; private set; }
    public IList<string> Tags { get; set; }            
}

这样的问题

我已经定义了样品采集：

I have defined sample collection of such questions:

var q1 = new Question("q1") { Tags = new List<string>() {"a"} };
var q2 = new Question("q2") { Tags = new List<string>() {"b"} };
var q3 = new Question("q3") { Tags = new List<string>() {"a", "b", "c"} };
var q4 = new Question("q4") { Tags = new List<string>() {"a", "b"} };
var q5 = new Question("q5") { Tags = new List<string>() {"z"} };
var q6 = new Question("q6");
var questions = new List<Question>() {q1, q2, q3, q4, q5, q6};

现在，我需要找到所有问题，其中包含至少一个标签，从给定的子集。子集的定义如下：

Now I need to find all questions, which contains at least one tag, from given subset. Subset is defined below:

string[] tags = new[] {"a", "b"};

我期望的 Q1 Q2 Q3 和 Q4 即可返回。我用它来获得所需结果的查询是：

I expect q1, q2, q3 and q4 to be returned. The query which I use to get desired result is:

var questions = DocumentSession.Query<Question>().AsQueryable();
questions = GetQuestionsToContainingAtLeastOneTagFromSubset(questions, tags)
// some other query restrictions
var result = questions.ToList(); // (**)

这假设强加在我收集的限制的功能如下：

The function which suppose to impose restrictions on my collection is following:

private IQueryable<Question> GetQuestionsToContainingAtLeastOneTagFromSubset(IQueryable<Question> questions, IEnumerable<string> tags)
{
    var result = new List<Question>();
    foreach (var tag in tags)
    {
        var currentTag = tag;
        var resultForTag = questions.Where(x => x.Tags.Any(xTag => xTag == currentTag));
        result = result.Concat(resultForTag).ToList();
     }
     return result.GroupBy(x => x.Id).Select(grp => grp.First()).AsQueryable();
}

我觉得这是非常低效的。我想避免使用 .ToList（）提供的函数中。据我了解这个 .ToList（） EX pressions查询RavenDB并返回我的部分结果（顺便说一句：我是吧？）。这是效率不高。我只是想强加在所提供的功能的限制，并执行查询后，所有的限制始终存在。该（**）的地方是为我好，以发送批量RavenDB检索查询结果。

I think this is highly inefficient. I'd like to avoid using .ToList() inside the provided function. As I understand this .ToList() expressions queries the RavenDB and returns me partial results (BTW: am I right ?). This is not efficient. I only want to impose restrictions in the provided function, and execute the query after all of the restrictions are imposed. The (**) place is good for me to sent the batch to RavenDB retrieve query result.

如何提高呢？

推荐答案

您可以查询Lucene来获得相匹配侑标签阿雷阵列像这样的标签问题：

You can query lucene to get the questions with tags that match yor tag aray array something like this:

string[] tags = new[] { "a", "b" };
string queryRange = "(" + string.Join(" OR ", tags) + ")";

var res = session.Advanced.LuceneQuery<Question>()
               .Where("Tags:" + queryRange).ToList();

请注意，此查询整个索引的问题，而不是一个子集。但我认为你可以追加 - 我想 - 要查询字符串EX pression。 见Lucene的文档获取更多关于这种类型的查询： 的http://lucene.apache.org/core/old_versioned_docs/versions/3_0_0/queryparsersyntax.html

Note that this queries the entire indexed questions, not a subset. But I think you can append - I GUESS - to the query string expression. See Lucene docs for more about these kind of queries: http://lucene.apache.org/core/old_versioned_docs/versions/3_0_0/queryparsersyntax.html

这篇关于发现其中包含由子集使用RavenDB和LINQ的至少一种元素的对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！