For an overview, see *Ditto Basics *> CRUD Fundamentals.

Use the write command to upsert, update, and remove documents from the Big Peer.

Do *not *include a find query within a write command in a single operation. Instead, perform each as separate API calls. For instructions, see Performing Find and Write Operations.

Once changes are made to the Big Peer, those changes then propagate to all Small Peers connected to the mesh network.

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Write Endpoint

To access Ditto’s HTTP API, direct your write requests to the following URL endpoint, making sure to replace {app_id} with the ID Ditto generated when you created your app in the portal.

For instructions on how to get your app ID, see Get Started.

https://{app_id}.cloud.ditto.live/api/v4/store/write

​
Upsert

The following snippet demonstrates how to use the curl command to perform a complete upsert operation to explicitly create or replace a document.

In this example, a friends key contains a register of the array type, alongside orderCount which functions as a counter.

For more information about registers and counters, see the Platform Manual > Data Types.

cURL
curl -X POST 'https://{app_id}.cloud.ditto.live/api/v4/store/write' \
  --header 'Content-Type: application/json' \
  --header 'Authorization: Bearer $API_KEY' \
  --data-raw '{
      "commands": [{
        "method": "upsert",
        "collection": "people",
        "id": "123abc",
        "value": {
          "name": "John",
          "friends": ["Susan"],
          "orderCount": 5
        }
      }]
  }'

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Specifying Types

When invoking upsert, use the valueTypeOverrides payload to create or modify a mutable type, such as a register map or a counter, in your request. For example, instead of using the default type, you explicitly specify to create a counter instead.

In Ditto, an array behaves as a register by default. This means you do not need to explicitly specify an array as a register in your request.

For more information, see the Platform Manual > REGISTER.

cURL
curl -X POST 'https://{app_id}.cloud.ditto.live/api/v4/store/write' \
  --header 'Content-Type: application/json' \
  --header 'Authorization: Bearer $API_KEY' \
  --data-raw '{
      "commands": [{
        "method": "upsert",
        "collection": "people",
        "id": "123abc",
        "value": {
          "name": "John",
          "friends": ["Susan"],
          "orderCount": 5
        },
        "valueTypeOverrides": {
          "orderCount": "counter",
          "friends": "register"
        }
      }]
  }'

​
Update Subcommands

When using update to make changes in the Big Peer, you can include any of the following subcommands within your update command to perform specific actions:

SubcommandDescription
setSets a specific value for a given field property.
incrementIncrements the value of a counter.
replaceWithCounterReplaces the current value with the counter.
https://{app_id}.cloud.ditto.live/api/v4/store/findbyid

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Remove

Use the remove command to delete documents from the Big Peer and all Small Peers connected in the mesh network.

Once deleted, Ditto indicates a document’s removal by creating a tombstone document. A tombstone contains metadata indicating that the associated data has been removed. Ditto creates a single tombstone for each document ID that matches the specified query.

To ensure that all Small Peers connected in the mesh network are aware that the document has been deleted, the tombstone, once created, triggers a change event that propagates across the mesh network as a record of its removal.

Although each tombstone document is not very large, there is no way to evict or remove them, so over time, if a user keeps doing removeoperations, tombstones will be an “invisible” source of disk usage with no upper bound.

For this reason, we strongly encourage the use of evict (combined with a thoughtful subscription and soft-delete strategy) instead. Learn more about EVICT.

For example, the following snippet demonstrates how to remove a document from the people collection where the name field is set to the value of John:

cURL
curl -X POST 'https://{app_id}.cloud.ditto.live/api/v4/store/write' \
  --header 'Authorization: Bearer $API_KEY' \
  --header 'Content-Type: application/json' \
  --data-raw '{
    "commands": [{
        "method": "remove",
        "collection": "people",
        "query": "name==\'John\'"
     }]
}'

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