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Description

MongoDB Error 55, 'Invalid D B Ref', indicates that a `DBRef` object used in an operation or stored in a document is malformed or points to an invalid location. This error typically occurs when the `DBRef` structure is incomplete, has incorrect field types, or refers to a non-existent collection or database.

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Error Message

Invalid D B Ref

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Known Causes

3 known causes

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Malformed DBRef Object Structure

The `DBRef` object is missing required fields like `$ref` (collection name) or `$id` (document ID), or has them in an incorrect format.

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Non-existent Referenced Collection or Database

The `DBRef` points to a collection or database that does not exist within the MongoDB deployment.

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Incorrect Data Type for DBRef Field

A field intended to store a `DBRef` object contains a value of an incompatible data type, preventing proper interpretation.

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Solutions

3 solutions available

1. Correct Invalid DBRef Structure easy

Ensures DBRefs are correctly formatted with '$ref', '$id', and optionally '$db'.

1

Identify documents containing the problematic DBRef. You can use a query to find documents where the field intended to be a DBRef does not conform to the expected structure. Common issues include missing '$ref' or '$id' fields.

db.collection.find({
  'your_dbref_field': { $not: { $type: 'object' } } 
})

2

Manually reconstruct the DBRef in the correct format. A valid DBRef is a document containing at least '$ref' (the collection name) and '$id' (the document's `_id`). You can also include '$db' if referencing a document in a different database.

db.collection.updateMany(
  { 'your_dbref_field': { $exists: true, $not: { '$ref': { $exists: true }, '$id': { $exists: true } } } },
  [
    {
      $set: {
        'your_dbref_field': {
          '$ref': 'target_collection_name',
          '$id': '$some_id_value',
          '$db': 'target_database_name' // Optional
        }
      }
    }
  ]
)

3

Verify the correction by querying the updated documents and checking the structure of the DBRef field.

db.collection.findOne({'_id': 'your_document_id'})

2. Remove or Re-evaluate Invalid DBRefs medium

Removes or replaces documents with malformed DBRefs if they are not critical or can be recreated.

1

Determine which documents contain invalid DBRefs that are causing the error. This might involve reviewing application logs or performing targeted queries.

db.collection.find({
  'your_dbref_field': { $type: 'object', $not: { '$ref': { $exists: true }, '$id': { $exists: true } } }
})

2

If the invalid DBRefs are not essential, consider removing them. This is a quick fix but might lead to data loss if the references are important.

db.collection.updateMany(
  { 'your_dbref_field': { $type: 'object', $not: { '$ref': { $exists: true }, '$id': { $exists: true } } } },
  { $unset: { 'your_dbref_field': '' } }
)

3

Alternatively, if the invalid DBRefs can be recreated, you might need to update the documents with valid data. This could involve re-inserting related data or manually populating the correct DBRef structure.

// Example: Recreating a DBRef after re-inserting the referenced document
db.collection.updateOne(
  { '_id': 'your_document_id' },
  { $set: { 'your_dbref_field': { '$ref': 'new_target_collection', '$id': 'new_referenced_id' } } }
)

3. Address Application Logic Errors advanced

Corrects the application code that is incorrectly constructing or handling DBRefs.

1

Review the application code responsible for creating and querying DBRefs. Look for instances where DBRefs are being constructed without the required '$ref' and '$id' fields, or where data types are mismatched.

// Example of incorrect DBRef creation in application code (pseudo-code)
const invalidRef = { collection: 'users', userId: '123' }; // Missing '$ref' and '$id'
db.collection.insertOne({ 'refField': invalidRef });

2

Modify the application logic to ensure that DBRefs are always created in the correct format. This typically involves using a library or helper function that correctly generates the DBRef document.

// Example of correct DBRef creation in application code (pseudo-code)
const correctRef = { '$ref': 'users', '$id': ObjectId('your_user_id_here') };
db.collection.insertOne({ 'refField': correctRef });

3

If the application is querying DBRefs, ensure that the query is also correctly handling the DBRef structure and not making assumptions about its format.

// Example of correct DBRef query (pseudo-code)
db.collection.find({ 'refField.$ref': 'users', 'refField.$id': ObjectId('your_user_id_here') });

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Related Errors

5 related errors

MongoDB Error 55: Invalid DB Reference