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Additionally, it offers support for various data types. For an overview of the data types you can use in Ditto, see the Platform Manual Data Structures and Types. A document serves as a schema-flexible unit of data. If collections are compared to tables, a document can be compared to a row. Each document at its core is a map capable of holding fields and embedded key-value pairs. Every document is assigned a primary key, referred to as a document ID. For more information about Ditto documents, see Platform Manual Document Model.

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Primary Key: Document ID

The Ditto query engine supports various filter operations for optimal data retrieval. As the basis of data organization and access in Ditto, the query engine indexes the document ID so you can quickly and precisely access your data. When invoking the Upsert method to create a new document, unless manually supplied, Ditto automatically generates and assigns the new document a 128‑bit Universally Unique Identifier (UUID).
When referencing the document ID in your queries for the HTTP API, pass id instead of the reserved _id parameter. However, if not making API calls, pass the reserved _id instead.

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Custom Document ID

If supplying your own document ID, you can encode your value in a string or, if forming a composite key, a JSON-object.
You can configure a custom document ID only at the time of document creation.Once a document is created, to ensure consistency and uniqueness throughout the platform, the unique identifier that either Ditto automatically generated and assigned or you manually assigned becomes permanent and cannot be changed at a later time.
The decision to opt for a composite key depends on your specific use case. Following are typical use cases for forming a composite key:
  • To implement additional logic to handle (or prevent) duplicate writes.
  • To simplify queries and enhance efficiency in the querying process.

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Supplying a String ID

To provide a custom document ID, when invoking upsert to create a new document, include the id parameter with a string set to the value you want to use as the document’s ID. For example, the following snippet demonstrates creating a new document in the people collection with the custom ID set to abc123, along with the specified name and age values:
cURL
curl -X POST 'https://<CLOUD_ENDPOINT>/api/v4/store/write' \
  --header 'Content-Type: application/json' \
  --data-raw '{
      "commands": [{
        "method": "upsert",
        "collection": "people",
        "id": "abc123",
        "value": {
          "name": "Susan", "age": 31
        }
      }]
  }'

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Forming a Composite Key

To form a composite key, when calling upsert to create a new document, pass the fields you want to combine to form the new primary key in an embedded map structure under the id field. For example, the following snippet shows an upsert operation on the people collection forming a composite key made up of two parts:
  • string
  • integer
Ditto compares document IDs based on the combination of keys and their corresponding values, not by literal order in which the key-value pairs are defined.Therefore, if two document IDs have the same key-value pairs, they will be considered equal. For example: {a: "foo", b: 1} == { b: 1, a: "foo" }
cURL
curl -X POST 'https://<CLOUD_ENDPOINT>/api/v4/store/write' \
  --header 'Content-Type: application/json' \
  --data-raw '{
      [{
        "method": "upsert",
        "collection": "people",
        "id": {
          "user_id": "456abc",
          "work_id": 789
        },
        "value": {
          "name": "Susan",
          "age": 31
        }
      }]
  }'