項目BsonDocument不查詢集合

Question

如何在不查詢集合的情況下將一個BsonDocument投影到新實例？

輸入：BsonDocument，new string[] { "_id", "meta.name", "type" }

輸出：BsonDocument僅填充上述元素

Answer 1

癢劃傷

輸入

{ 
    "_id" : ObjectId("58b454f40960a1788ef48ebc"), 
    "schema" : { 
    "id" : "asset", 
    "version" : { 
     "major" : 1, 
     "minor" : 0 
    } 
    }, 
    "type" : "asset", 
    "meta" : { 
    "name" : "Most Amazing Product", 
    "type" : null, 
    "legacy" : { 
     "url" : "https://s3.amazonaws.com/bucket_name/guid" 
    } 
    }, 
    "content" : { 
    "is_s3" : true, 
    "s3_bucket" : "bucket_name", 
    "s3_key" : "guid.doc", 
    "url" : "https://s3.amazonaws.com/guid.doc" 
    }, 
    "modified-date" : ISODate("2017-08-09T15:25:57.972Z"), 
    "modified-by" : "api" 
} 

代碼

nuget: MongoDB.Driver 2.4.4 
using MongoDB.Bson; 
using MongoDB.Bson.Serialization; 
using MongoDB.Bson.IO; 

BsonDocument original = BsonDocument.Parse(@"{ ""_id"" : ObjectId(""58b454f40960a1788ef48ebc""), ""schema"" : { ""id"" : ""asset"", ""version"" : { ""major"" : 1, ""minor"" : 0 } }, ""type"" : ""asset"", ""meta"" : { ""name"" : ""Most Amazing Product"", ""type"" : null, ""legacy"" : { ""url"" : ""https://s3.amazonaws.com/bucket_name/guid"" } }, ""content"" : { ""is_s3"" : true, ""s3_bucket"" : ""bucket_name"", ""s3_key"" : ""guid.doc"", ""url"" : ""https://s3.amazonaws.com/guid.doc"" }, ""modified-date"" : ISODate(""2017-08-09T15:25:57.972Z""), ""modified-by"" : ""api"" }"); 

string[] fields = new[] { "_id", "meta.name", "type" }; 

BsonDocument projection = new BsonDocument(); 
foreach (var fieldName in fields) 
{ 
    BsonDocument source = original; 
    BsonDocument target = projection; 
    string[] parts = fieldName.Split(new[] { "." }, StringSplitOptions.RemoveEmptyEntries); 
    for (int i = 0; i < parts.Length; i++) 
    { 
     string currentName = parts[i]; 
     if (i == parts.Length - 1) 
     { 
      if(source.Contains(currentName)) 
       target[currentName] = source[currentName]; 
     } 
     else 
     { 
      // Does the source have a current property at this level 
      if (source.Contains(currentName)) 
      { 
       // first time this has been visited on target 
       if (target.Contains(currentName) == false) 
       { 
        target.Add(currentName, new BsonDocument()); 
       } 
       source = source[currentName] as BsonDocument; 
       target = target[currentName] as BsonDocument; 
      } 
      else 
      { 
       // no need to go any further if the source doesn't have the property specified 
       break; 
      } 
     } 
    } 
} 

結果

{ 
    "_id" : ObjectId("58b454f40960a1788ef48ebc"), 
    "meta" : { 
    "name" : "Most Amazing Product" 
    }, 
    "type" : "asset" 
}