Question

此问题涉及How to project specific fields in array on filtered lookup中的示例过滤器应用于＆＃39;加入＆＃39;表。现在我想将其转换为C＃中的查询，但我没有设法将过滤器添加到投影中。这是我得到的：

db.GetCollection("meta")
.Aggregate()
.Match(new BsonDocument { { "test", "OK" }})
.Lookup("merge","Exp","Exp","kin")
.Project(Builders<BsonDocument>.Projection
         .Include("Exp") 
         .Include("test")
         .Include("kin")
 )

有什么想法吗？

Answer 1

似乎工作艰难：

db.GetCollection("meta")
.Aggregate()
.Match(new BsonDocument { { "test", "OK" }})
.Lookup("merge","Exp","Exp","kin")
.Project(new BsonDocument {
    { "Exp" , 1},
    { "test" , 1},
    { "kin", new BsonDocument {   
        { "$filter", new BsonDocument { 
            { "input", "$kin"},
            { "as",  , "kin"},
            { "cond",  new BsonDocument {
                { "$eq", new BsonArray { "$$kin.M2", "val"}}}
            }}
        }}
    }})
  .Project(new BsonDocument {
    { "Exp", 1 },
    {"test", 1},
    {"date", 1},
    {"kin.M1",1},
    {"kin.M2",1}, 
    {"kin.T",1 }})

但当然使用Mongo Driver的API会很好。

MongoDB在C＃中过滤查找

1 个答案: