CODEWITHSUNDEEP
c#mongodbguid
AdamS
AdamS

Reputation: 73

How to query MongoDb for partial Id matches with Guid Id?

I have an App written in C#, where the DB is MongoDB. the Id object is C# Guid, so the _id field in the DB looks like:


  "_id": {
    "$binary": {
      "base64": "tZqfm0KNMUi1GGfCkQQosw==",
      "subType": "03"
    }
  }

And the App is using regular Guid ("9b9f9ab5-8d42-4831-b518-67c2910428b3")

Now, I want to add the ability to search by partial id - if I search for "67c2910428b3", I want to find the object with corresponding id.

how to I add a filter \ query to do that ?

I cannot use BsonRegex, since the field in the db is not "converted" - it will never get Guid-id.

the "simple" solution is to add another field in MongoDB with the Guid as string so i can Search on it - but that seems redundant, since the id is already there.

Upvotes: 2

Views: 866

Answers (1)

Joe
Joe

Reputation: 28336

From the bson spec, binary subtype 3 is the old UUID format. One of the problems with the old format was that it permitted the client to specify the ordering of the bytes.

Decoding from the base-64 string, the value of that field is:

0xb59a9f9b428d3148b51867c2910428b3

Note that this UUID you mention, but is using a client ordering that does not conform to RFC-4122 section 4.1.2, which requires MSB ordering for each field.

A UUID is stored by MongoDB as a binary blob. There are no server-side functions to convert or slice the value into smaller chunks.

You can make comparisons of the entire value as described in Comparison/Sort Order

For example, you could find all values that start with 9b9f9ab5 by querying for

{$gte: Guid("9b9f9ab5-0000-0000-0000-000000000000"), $lt: Guid("9b9f9ab6-0000-0000-0000-000000000000")}

Querying a part in the middle, such as all UUID with a time-mid value of 0x8d42 like 00000000-8d42-0000-0000-000000000000, will not be possible with the value stored as binary.

Upvotes: 2

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