[英]Searching an array of objects in MongoDB using the C# Driver
Following the advice of this article I created a blob index on an array of objects in my documents. 按照本文的建议,我在文档中的对象数组上创建了一个Blob索引。 For example: 例如:
{
...
"itemID" : 37,
"MetaData" : [
{
"FileExtension" : "TXT"
},
{
"EmailSubject" : "GAS DESK HEAD MEETING"
},
{
"DocumentType" : "EMAIL"
},
{
"Date_BestEmailSent" : ISODate("2001-01-26T04:11:32.000Z")
},
{
"Date_ParentDate_BestDate" : ISODate("2001-01-26T04:11:32.000Z")
},
...
],
...
}
I'm now parsing a search tree in C# to build a query using the MongoDB C# driver: 我现在正在解析C#中的搜索树,以使用MongoDB C#驱动程序来构建查询:
IMongoQuery expression;
switch (leaf.Op)
{
case SearchOperation.Equals:
expression = Query.EQ(leaf.Field, leaf.Value);
break;
case SearchOperation.Contains:
expression = Query.Matches(leaf.Field, leaf.Field);
break;
...
}
if (_rootLevelFields.Contains(leaf.Field))
{
return expression;
}
return Query.ElemMatch("MetaData", expression);
In this case, if my search criteria was FileExtension EQ 'TXT'
It would run: 在这种情况下,如果我的搜索条件是FileExtension EQ 'TXT'
,它将运行:
db.test.find({"MetaData": {$elemMatch: {"FileExtension":"TXT"}}})
This runs very slowly and the explain indicates it's scanning all records and not using my Index. 这运行非常缓慢,并且解释说明它正在扫描所有记录,而不使用我的索引。 If I manually run: 如果我手动运行:
db.test.find({"MetaData": {"FileExtension":"TXT"}})
It uses the index and runs much faster. 它使用索引并且运行更快。 In this case it appears I don't want to use ElemMatch but the MongoDB Builder namespace doesn't seem to accommodate this type of query eg 在这种情况下,我似乎不想使用ElemMatch,但是MongoDB Builder命名空间似乎无法容纳这种查询,例如
Query.EQ("MetaData", expression);
is not syntactically correct. 在语法上不正确。 I've poured over the documentation and even the MongoDB driver source code but can't find how to do what I want. 我已经遍历了文档甚至MongoDB驱动程序源代码,但是找不到如何做我想要的事情。 Am I missing something obvious? 我是否缺少明显的东西?
The EQ
method accepts only BSONValue
as a parameter, but you're trying to pass a IMongoQuery
instance. EQ
方法仅接受BSONValue
作为参数,但是您正在尝试传递IMongoQuery
实例。
In your second query you're basically searching this document in MetaData
array : 在第二个查询中,您基本上是在MetaData
数组中搜索此文档:
{"FileExtension":"TXT"}
You will need to create a new BsonDocument and pass it into your EQ
method: 您将需要创建一个新的BsonDocument并将其传递到您的EQ
方法中:
Query.EQ("MetaData", new BsonDocument(leaf.Field, leaf.Value));
You can check the documentation for EQ method for more details. 您可以查看EQ方法的文档以了解更多详细信息。
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