c# - MongoDB - 无法规范化查询

Question

我正在尝试使用 C# 驱动程序 (1.9.0) 和范围变量在集合上运行 mapreduce。我使用以下代码:

var map = @"function() {
    emit(this._id, foo); 
};";

var reduce = @"function(key, values) { 
    return values; 
};";

var options = new MapReduceOptionsBuilder();
options.SetOutput(MapReduceOutput.Inline);
options.SetScope(new ScopeDocument("foo", "foo"));

当我使用这段代码时，出现以下异常:

An exception of type 'MongoDB.Driver.MongoCommandException' occurred in MongoDB.Driver.dll but was not handled in user code

Additional information: Command 'mapreduce' failed: exception: Can't canonicalize query {} (response: { "errmsg" : "exception: Can't canonicalize query {}", "code" : 17238, "ok" : 0.0 })

如果我像下面那样删除范围变量，它会起作用:

var map = @"function() {
    //emit(this._id, foo); 
    emit(this._id, 1); 
};";

var reduce = @"function(key, values) { 
    return values; 
};";

var options = new MapReduceOptionsBuilder();
options.SetOutput(MapReduceOutput.Inline);
//options.SetScope(new ScopeDocument("foo", "foo"));

有谁知道这是错的吗？

Answer 1

我找到了解决方案。事实证明我必须使用 BsonJavaScriptWithScope 而不是 SetScope。

var map = @"function() {
    emit(this._id, foo); 
};";

var reduce = @"function(key, values) { 
    return values; 
};";

var scope = new BsonDocument("foo", "foo");

var args = new MapReduceArgs()
{
    MapFunction = new BsonJavaScriptWithScope(map, scope),
    ReduceFunction = new BsonJavaScript(reduce),
    OutputMode = MapReduceOutputMode.Inline
};  

var results = collection.MapReduce(args).GetResults();