How to handle missing References

Introduction

In dcupl, managing references between models can be challenging, especially if data quality varies. There are several strategies to handle missing references, tailored to specific use cases or requirements.

Validity

When dealing with references, you have the option to set their validity as either strict or loose. With a loose reference, the value is retained even if the target is not found. On the other hand, a strict reference turns to undefined when its target is missing. The choice of validity should align with the needs of your application.

{
  "key": "modelA",
  "references": [
    {
      "key": "b_loose",
      "model": "modelB",
      "type": "singleValued",
      "validity": "loose"
    },
    {
      "key": "b_strict",
      "model": "modelB",
      "type": "singleValued",
      "validity": "strict"
    }
  ]
}

// if a.b_loose points to a missing reference the value of b_loose remains an object
{ "key": "a1", "b_loose": { "key": "some_missing_key" } }

// if a.b_strict points to a missing reference it's value is undefined
{ "key": "a1" } // b_strict is not present since it's undefined

Reference Metadata

When you activate reference metadata in your project, dcupl enhances your references with an additional parameter. This parameter indicates the status of the reference as either a hit, miss, or auto_hit (the latter denotes a successful reference generated from a "supportsAutogeneration" action). Utilizing reference metadata is particularly beneficial when working with loose references, as it provides clearer insights into the reference's resolution status.

const dcupl = new Dcupl({
  referenceMetadata: {
    enabled: true,
  },
});

Using the same model as above the responses looks like this:

// if a.b_loose points to a missing reference the value of b_loose remains an object
[
  {
    "key": "a1",
    "b_loose": { "key": "some_missing_key", "_dcupl_ref_": "miss" }
  },
  {
    "key": "a2",
    "b_loose": { "key": "valid_key", "_dcupl_ref_": "hit" }
  },
]

An Example query for "missed References" might looks like this:

const q = dcupl.query.generate('modelA', {
  attribute: 'b_loose',
  operator: 'find',
  value: { _dcupl_ref_: 'miss' },
});
const missing_b_Loose = dcupl.query.execute(q);