使用C#驱动程序从MongoDB集合上的文本查询检索相关性排序结果 [英] Retrieve Relevance Ordered Result from Text Query on MongoDB Collection using the C# Driver

问题描述

我正在尝试对集合进行文本查询，并以文本匹配顺序检索结果. 文档很好地解释了如何在shell中执行此操作:

I am attempting to text query a collection and retrieve the results in the text match order. The docs explain pretty well how to do this in the shell:

db.articles.find(
   { status: "A", $text: { $search: "coffee cake" } },
   { score: { $meta: "textScore" } }
).sort( { date: 1, score: { $meta: "textScore" } } )

，但它需要将查找中的其他score字段投影到排序中.

but it requires the projection of the additional score field from the find into the sort.

在C#中，我有一个看起来像这样的函数:

In C#, I have a function that looks like this:

public IEnumerable<T> TextSearch<T>(MongoCollection<T> coll, string text) {
    var cursor = coll.Find(Query.Text(text))
        .SetSortOrder(SortBy<T>.MetaTextScore(???));
    foreach(var t in cursor) {
        // strip projected score from value
        yield return t;
    }
}

但是我不知道如何将"textScore"值投影到我的结果中，这样我就可以

but I am missing how to project the "textScore" value into my results, so that I can specify the column to MetaTextScore in SetSortOrder.

推荐答案

我能够通过反复试验来解决这个问题.诀窍是您的数据对象已经需要在其上具有一个字段，该字段将保存MetaTextScore值.因此，给定接口:

I was able to get this working through trial and error. The trick is that your data object needs to have a field on it already that will hold the MetaTextScore value. So given the interface:

interface ITextSearchSortable {
    double? TextMatchScore { get; set; }
}

最终功能如下:

public IEnumerable<T> TextSearch<T>(MongoCollection<T> coll, string text) where T:ITextSearchSortable {
    var cursor = coll.Find(Query.Text(text))
        .SetFields(Fields<T>.MetaTextScore(t => t.TextMatchScore))
        .SetSortOrder(SortBy<T>MetaTextScore(t => t.TextMatchScore));
    foreach(var t in cursor) {
        // prevent saving the value back into the database
        t.TextMatchScore = null;
        yield return t;
    }
}

值得注意的是，TextMatchScore不能具有[BsonIgnore]装饰，否则会出现异常.但是，它可以具有[BsonIgnoreIfNull]装饰.因此，通过在产生数据对象之前清除该数据对象的值，可以将该数据对象保存回集合中，而无需放入垃圾值.

It's worth noting that TextMatchScore can't have a [BsonIgnore] decoration, or there will be an exception. However, it can have a [BsonIgnoreIfNull] decoration. So by scrubbing the value off the data object before yielding it, the data object can be saved back into the collection without putting in a garbage value.

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